diff --git a/src/pymcnp/files/inp/datum.py b/src/pymcnp/files/inp/datum.py
index d19b36d..d7de0cb 100644
--- a/src/pymcnp/files/inp/datum.py
+++ b/src/pymcnp/files/inp/datum.py
@@ -7866,6 +7866,1122 @@ def __init__(self, mnemonic: Datum.DatumMnemonic, parameters: tuple[any]):
         self.parameters = parameters
 
 
+class SourceDefinition(Datum):
+    """
+    ``SourceDefinition`` represents INP nps data cards.
+
+    ``SourceDefinition`` inherits attributes from ``Datum``. It represents the
+    INP model physics source definition data card syntax element.
+
+    Attributes:
+        pairs: Tuple of key-value pairs.
+    """
+
+    class SourceDefinitionOption:
+        """
+        ``SourceDefinitionOption`` represents INP source definition data card
+        options.
+
+        ``SourceDefinitionOption`` implements INP source definition data card
+        options. Its attributes store keywords and values, and its methods
+        provide entry and endpoints for working with INP source definition
+        data card options. It represents the generic INP source definition
+        data card option syntax element, so ``SourceDefinition`` depends on
+        ``SourceDefinitionOption`` as a generic data structure and superclass.
+
+        Attributes:
+            keyword: Activation control data card option keyword.
+            value: Activation control data card option value.
+        """
+
+        class SourceDefinitionKeyword(StrEnum):
+            """
+            ``SourceDefinitionKeyword`` represents INP source definition data
+            card keywords.
+
+            ``SourceDefinitionKeyword`` implements INP source definition data
+            card keywords as a Python inner class. It enumerates MCNP keywords
+            and provides methods for casting strings to
+            ``SourceDefinitionKeyword`` instances. It represents the INP
+            source definition data card keyword syntax element, so
+            ``SourceDefinition`` and ``SourceDefinitionOption`` depend on
+            ``SourceDefinitionKeyword`` as an enum.
+            """
+
+            CEL = "cel"
+            SUR = "sur"
+            ERG = "erg"
+            TME = "tme"
+            DIR = "dir"
+            VEC = "vec"
+            NRM = "nrm"
+            POS = "pos"
+            RAD = "rad"
+            EXT = "ext"
+            AXS = "axs"
+            X = "x"
+            Y = "y"
+            Z = "z"
+            CCC = "ccc"
+            ARA = "ara"
+            WGT = "wgt"
+            TR = "tr"
+            EFF = "eff"
+            PAR = "par"
+            DAT = "dat"
+            LOC = "loc"
+            BEM = "bem"
+            BAP = "bap"
+
+            @staticmethod
+            def from_mcnp(source: str):
+                """
+                ``from_mcnp`` generates ``SourceDefinitionKeyword`` objects
+                from INP.
+
+                ``from_mcnp`` constructs instances of
+                ``SourceDefinitionKeyword`` from INP source strings, so it
+                operates as a class constructor method and INP parser helper
+                function.
+
+                Parameters:
+                    source: INP for source definition option keyword.
+
+                Returns:
+                    ``SourceDefinitionKeyword`` object.
+
+                Raises:
+                    MCNPSemanticError: INVALID_DATUM_SOURCE_KEYWORD.
+                """
+
+                source = _parser.Preprocessor.process_inp(source)
+
+                # Processing Keyword
+                if source not in [enum.value for enum in SourceDefinition.SourceDefinitionOption.SourceDefinitionKeyword]:
+                    raise errors.MCNPSemanticError(errors.MCNPSemanticCodes.INVALID_DATUM_SOURCE_KEYWORD)
+
+                return SourceDefinition.SourceDefinitionOption.SourceDefinitionKeyword(source)
+
+        def __init__(self, keyword: SourceDefinitionKeyword, value: any):
+            """
+            ``__init__`` initializes ``SourceDefinitionOption``.
+
+            Parameters:
+                keyword: Source definition data card option keyword.
+                value: Source definition data card option value.
+
+            Raises:
+                MCNPSemanticError: INVALID_DATUM_SOURCE_KEYWORD.
+            """
+
+            if keyword is None:
+                raise errors.MCNPSemanticError(errors.MCNPSemanticCodes.INVALID_DATUM_SOURCE_KEYWORD)
+
+            match keyword:
+                case SourceDefinition.SourceDefinitionOption.SourceDefinitionKeyword.CEL:
+                    obj = SourceDefinition.Cel(value)
+                case SourceDefinition.SourceDefinitionOption.SourceDefinitionKeyword.SUR:
+                    obj = SourceDefinition.Sur(value)
+                case SourceDefinition.SourceDefinitionOption.SourceDefinitionKeyword.ERG:
+                    obj = SourceDefinition.Erg(value)
+                case SourceDefinition.SourceDefinitionOption.SourceDefinitionKeyword.TME:
+                    obj = SourceDefinition.Tme(value)
+                case SourceDefinition.SourceDefinitionOption.SourceDefinitionKeyword.DIR:
+                    obj = SourceDefinition.Dir(value)
+                case SourceDefinition.SourceDefinitionOption.SourceDefinitionKeyword.VEC:
+                    obj = SourceDefinition.Vec(value)
+                case SourceDefinition.SourceDefinitionOption.SourceDefinitionKeyword.NRM:
+                    obj = SourceDefinition.Nrm(value)
+                case SourceDefinition.SourceDefinitionOption.SourceDefinitionKeyword.POS:
+                    obj = SourceDefinition.Pos(value)
+                case SourceDefinition.SourceDefinitionOption.SourceDefinitionKeyword.RAD:
+                    obj = SourceDefinition.Rad(value)
+                case SourceDefinition.SourceDefinitionOption.SourceDefinitionKeyword.EXT:
+                    obj = SourceDefinition.Ext(value)
+                case SourceDefinition.SourceDefinitionOption.SourceDefinitionKeyword.AXS:
+                    obj = SourceDefinition.Axs(value)
+                case SourceDefinition.SourceDefinitionOption.SourceDefinitionKeyword.X:
+                    obj = SourceDefinition.X(value)
+                case SourceDefinition.SourceDefinitionOption.SourceDefinitionKeyword.Y:
+                    obj = SourceDefinition.Y(value)
+                case SourceDefinition.SourceDefinitionOption.SourceDefinitionKeyword.Z:
+                    obj = SourceDefinition.Z(value)
+                case SourceDefinition.SourceDefinitionOption.SourceDefinitionKeyword.CCC:
+                    obj = SourceDefinition.Ccc(value)
+                case SourceDefinition.SourceDefinitionOption.SourceDefinitionKeyword.ARA:
+                    obj = SourceDefinition.Ara(value)
+                case SourceDefinition.SourceDefinitionOption.SourceDefinitionKeyword.WGT:
+                    obj = SourceDefinition.Wgt(value)
+                case SourceDefinition.SourceDefinitionOption.SourceDefinitionKeyword.TR:
+                    obj = SourceDefinition.Tr(value)
+                case SourceDefinition.SourceDefinitionOption.SourceDefinitionKeyword.EFF:
+                    obj = SourceDefinition.Eff(value)
+                case SourceDefinition.SourceDefinitionOption.SourceDefinitionKeyword.PAR:
+                    obj = SourceDefinition.Par(value)
+                case SourceDefinition.SourceDefinitionOption.SourceDefinitionKeyword.DAT:
+                    obj = SourceDefinition.Dat(value)
+                case SourceDefinition.SourceDefinitionOption.SourceDefinitionKeyword.LOC:
+                    obj = SourceDefinition.Loc(value)
+                case SourceDefinition.SourceDefinitionOption.SourceDefinitionKeyword.BEM:
+                    obj = SourceDefinition.Bem(value)
+                case SourceDefinition.SourceDefinitionOption.SourceDefinitionKeyword.BAP:
+                    obj = SourceDefinition.Bap(value)
+
+            self.__dict__ = obj.__dict__
+            self.__class__ = obj.__class__
+
+        @staticmethod
+        def from_mcnp(source: str):
+            """
+            ``from_mcnp`` generates ``SourceDefinitionOption`` objects from
+            INP.
+
+            ``from_mcnp`` constructs instances of ``SourceDefinitionOption``
+            from INP source strings, so it operates as a class constructor
+            method and INP parser helper function. Although defined on the
+            superclass, it returns ``SourceDefinitionOption`` subclasses.
+
+            Parameters:
+                source: INP for activation option.
+
+            Returns:
+                ``SourceDefinitionOption`` object.
+
+            Raises:
+                MCNPSyntaxError: TOOFEW_DATUM_SOURCE.
+                MCNPSyntaxError: TOOLONG_DATUM_SOURCE.
+            """
+
+            source = _parser.Preprocessor.process_inp(source)
+            tokens = _parser.Parser(
+                re.split(r"=| ", source), errors.MCNPSyntaxError(errors.MCNPSyntaxCodes.TOOFEW_DATUM_SOURCE)
+            )
+
+            # Processing Keyword
+            keyword = SourceDefinition.SourceDefinitionOption.SourceDefinitionKeyword.from_mcnp(tokens.popl())
+
+            # Processing Values
+            match keyword:
+                case SourceDefinition.SourceDefinitionOption.SourceDefinitionKeyword.CEL:
+                    value = types.McnpInteger.from_mcnp(tokens.popl())
+                case SourceDefinition.SourceDefinitionOption.SourceDefinitionKeyword.SUR:
+                    value = types.McnpInteger.from_mcnp(tokens.popl())
+                case SourceDefinition.SourceDefinitionOption.SourceDefinitionKeyword.ERG:
+                    if tokens.peekl()[0] == "d":
+                        value = types.DistributionNumber.from_mcnp(tokens.popl())
+                    else:
+                        value = types.McnpReal.from_mcnp(tokens.popl())
+                case SourceDefinition.SourceDefinitionOption.SourceDefinitionKeyword.TME:
+                    value = types.McnpReal.from_mcnp(tokens.popl())
+                case SourceDefinition.SourceDefinitionOption.SourceDefinitionKeyword.DIR:
+                    if tokens.peekl()[0] == "d":
+                        value = types.DistributionNumber.from_mcnp(tokens.popl())
+                    else:
+                        value = types.McnpReal.from_mcnp(tokens.popl())
+                case SourceDefinition.SourceDefinitionOption.SourceDefinitionKeyword.VEC:
+                    value = (
+                        types.McnpReal.from_mcnp(tokens.popl()),
+                        types.McnpReal.from_mcnp(tokens.popl()),
+                        types.McnpReal.from_mcnp(tokens.popl()),
+                    )
+                case SourceDefinition.SourceDefinitionOption.SourceDefinitionKeyword.NRM:
+                    value = types.McnpInteger.from_mcnp(tokens.popl())
+                case SourceDefinition.SourceDefinitionOption.SourceDefinitionKeyword.POS:
+                    value = (
+                        types.McnpReal.from_mcnp(tokens.popl()),
+                        types.McnpReal.from_mcnp(tokens.popl()),
+                        types.McnpReal.from_mcnp(tokens.popl()),
+                    )
+                case SourceDefinition.SourceDefinitionOption.SourceDefinitionKeyword.RAD:
+                    if tokens.peekl()[0] == "d":
+                        value = types.DistributionNumber.from_mcnp(tokens.popl())
+                    else:
+                        value = types.McnpReal.from_mcnp(tokens.popl())
+                case SourceDefinition.SourceDefinitionOption.SourceDefinitionKeyword.EXT:
+                    value = types.McnpReal.from_mcnp(tokens.popl())
+                case SourceDefinition.SourceDefinitionOption.SourceDefinitionKeyword.AXS:
+                    value = (
+                        types.McnpReal.from_mcnp(tokens.popl()),
+                        types.McnpReal.from_mcnp(tokens.popl()),
+                        types.McnpReal.from_mcnp(tokens.popl()),
+                    )
+                case SourceDefinition.SourceDefinitionOption.SourceDefinitionKeyword.X:
+                    value = types.McnpReal.from_mcnp(tokens.popl())
+                case SourceDefinition.SourceDefinitionOption.SourceDefinitionKeyword.Y:
+                    value = types.McnpReal.from_mcnp(tokens.popl())
+                case SourceDefinition.SourceDefinitionOption.SourceDefinitionKeyword.Z:
+                    value = types.McnpReal.from_mcnp(tokens.popl())
+                case SourceDefinition.SourceDefinitionOption.SourceDefinitionKeyword.CCC:
+                    value = types.McnpInteger.from_mcnp(tokens.popl())
+                case SourceDefinition.SourceDefinitionOption.SourceDefinitionKeyword.ARA:
+                    value = types.McnpReal.from_mcnp(tokens.popl())
+                case SourceDefinition.SourceDefinitionOption.SourceDefinitionKeyword.WGT:
+                    value = types.McnpReal.from_mcnp(tokens.popl())
+                case SourceDefinition.SourceDefinitionOption.SourceDefinitionKeyword.TR:
+                    value = types.McnpInteger.from_mcnp(tokens.popl())
+                case SourceDefinition.SourceDefinitionOption.SourceDefinitionKeyword.EFF:
+                    value = types.McnpReal.from_mcnp(tokens.popl())
+                case SourceDefinition.SourceDefinitionOption.SourceDefinitionKeyword.PAR:
+                    value = tokens.popl()
+                case SourceDefinition.SourceDefinitionOption.SourceDefinitionKeyword.DAT:
+                    value = (
+                        types.McnpInteger.from_mcnp(tokens.popl()),
+                        types.McnpInteger.from_mcnp(tokens.popl()),
+                        types.McnpInteger.from_mcnp(tokens.popl()),
+                    )
+                case SourceDefinition.SourceDefinitionOption.SourceDefinitionKeyword.LOC:
+                    value = (
+                        types.McnpReal.from_mcnp(tokens.popl()),
+                        types.McnpReal.from_mcnp(tokens.popl()),
+                        types.McnpReal.from_mcnp(tokens.popl()),
+                    )
+                case SourceDefinition.SourceDefinitionOption.SourceDefinitionKeyword.BEM:
+                    value = (
+                        types.McnpReal.from_mcnp(tokens.popl()),
+                        types.McnpReal.from_mcnp(tokens.popl()),
+                        types.McnpReal.from_mcnp(tokens.popl()),
+                    )
+                case SourceDefinition.SourceDefinitionOption.SourceDefinitionKeyword.BAP:
+                    value = (
+                        types.McnpReal.from_mcnp(tokens.popl()),
+                        types.McnpReal.from_mcnp(tokens.popl()),
+                        types.McnpReal.from_mcnp(tokens.popl()),
+                    )
+
+            if tokens:
+                raise errors.MCNPSyntaxError(errors.MCNPSyntaxCodes.TOOLONG_DATUM_SOURCE)
+
+            return SourceDefinition.SourceDefinitionOption(keyword, value)
+
+        def to_mcnp(self):
+            """
+            ``to_mcnp`` generates INP from ``SourceDefinitionOption`` objects.
+
+            ``to_mcnp`` creates INP source string from ``SourceDefinitionOption``
+            objects, so it provides an MCNP endpoint.
+
+            Returns:
+                INP string for ``SourceDefinitionOption`` object.
+            """
+
+            return f"{SourceDefinition.SourceDefinitionOption.SourceDefinitionKeyword(self.keyword)}={self.value}"
+
+    class Cel(SourceDefinitionOption):
+        """
+        ``Cel`` represents INP Cel source definition data card
+        options.
+
+        ``Cel`` inherits attributes from ``SourceDefinitionOption``. It
+        represents the INP Cel source definition data card option syntax element.
+
+        Attributes:
+            number: Cell number.
+        """
+
+        def __init__(self, number: types.McnpInteger):
+            """
+            ``__init__`` initializes ``Cel``.
+
+            Parameters:
+                number: Cell number.
+
+            Raises:
+                MCNPSemanticError: INVALID_DATUM_SOURCE_VALUE.
+            """
+
+            if number is None or not (1 <= number <= 99_999_999):
+                raise errors.MCNPSemanticError(errors.MCNPSemanticCodes.INVALID_DATUM_SOURCE_VALUE)
+
+            self.keyword = SourceDefinition.SourceDefinitionOption.SourceDefinitionKeyword.CEL
+            self.value = number
+            self.number = number
+
+    class Sur(SourceDefinitionOption):
+        """
+        ``Sur`` represents INP Sur source definition data card
+        options.
+
+        ``Sur`` inherits attributes from ``SourceDefinitionOption``. It
+        represents the INP Sur source definition data card option syntax element.
+
+        Attributes:
+            number: Surface number.
+        """
+
+        def __init__(self, number: types.McnpInteger):
+            """
+            ``__init__`` initializes ``Sur``.
+
+            Parameters:
+                number: Surface number.
+
+            Raises:
+                MCNPSemanticError: INVALID_DATUM_SOURCE_VALUE.
+            """
+
+            if number is None or not (1 <= number <= 99_999_999):
+                raise errors.MCNPSemanticError(errors.MCNPSemanticCodes.INVALID_DATUM_SOURCE_VALUE)
+
+            self.keyword = SourceDefinition.SourceDefinitionOption.SourceDefinitionKeyword.SUR
+            self.value = number
+            self.number = number
+
+    class Erg(SourceDefinitionOption):
+        """
+        ``Erg`` represents INP Erg source definition data card
+        options.
+
+        ``Erg`` inherits attributes from ``SourceDefinitionOption``. It
+        represents the INP Erg source definition data card option syntax element.
+
+        Attributes:
+            energy: Kinetic energy.
+        """
+
+        def __init__(self, energy: Union[types.McnpReal, types.DistributionNumber]):
+            """
+            ``__init__`` initializes ``Erg``.
+
+            Parameters:
+                energy: Kinetic energy.
+
+            Raises:
+                MCNPSemanticError: INVALID_DATUM_SOURCE_VALUE.
+            """
+
+            if isinstance(energy, types.McnpReal):
+                if energy is None or not (energy >= 0):
+                    raise errors.MCNPSemanticError(errors.MCNPSemanticCodes.INVALID_DATUM_SOURCE_VALUE)
+            else:
+                if energy is None:
+                    raise errors.MCNPSemanticError(errors.MCNPSemanticCodes.INVALID_DATUM_SOURCE_VALUE)
+
+            self.keyword = SourceDefinition.SourceDefinitionOption.SourceDefinitionKeyword.ERG
+            self.value = energy
+            self.energy = energy
+
+    class Tme(SourceDefinitionOption):
+        """
+        ``Tme`` represents INP Tme source definition data card
+        options.
+
+        ``Tme`` inherits attributes from ``SourceDefinitionOption``. It
+        represents the INP Tme source definition data card option syntax element.
+
+        Attributes:
+            time: Time.
+        """
+
+        def __init__(self, time: types.McnpReal):
+            """
+            ``__init__`` initializes ``Tme``.
+
+            Parameters:
+                _
+
+            Raises:
+                MCNPSemanticError: INVALID_DATUM_SOURCE_VALUE.
+            """
+
+            if time is None:
+                raise errors.MCNPSemanticError(errors.MCNPSemanticCodes.INVALID_DATUM_SOURCE_VALUE)
+
+            self.keyword = SourceDefinition.SourceDefinitionOption.SourceDefinitionKeyword.TME
+            self.value = time
+            self.time = time
+
+    class Dir(SourceDefinitionOption):
+        """
+        ``Dir`` represents INP Dir source definition data card
+        options.
+
+        ``Dir`` inherits attributes from ``SourceDefinitionOption``. It
+        represents the INP Dir source definition data card option syntax element.
+
+        Attributes:
+            cosine: Cosine of the angle between VEC and particle's direction.
+        """
+
+        def __init__(self, cosine: Union[types.McnpReal, types.DistributionNumber]):
+            """
+            ``__init__`` initializes ``Dir``.
+
+            Parameters:
+                cosine: Cosine of the angle between VEC and particle's direction.
+
+            Raises:
+                MCNPSemanticError: INVALID_DATUM_SOURCE_VALUE.
+            """
+
+            if isinstance(cosine, types.McnpReal):
+                if cosine is None or not (-1 <= cosine <= 1):
+                    raise errors.MCNPSemanticError(errors.MCNPSemanticCodes.INVALID_DATUM_SOURCE_VALUE)
+            else:
+                if cosine is None:
+                    raise errors.MCNPSemanticError(errors.MCNPSemanticCodes.INVALID_DATUM_SOURCE_VALUE)
+
+            self.keyword = SourceDefinition.SourceDefinitionOption.SourceDefinitionKeyword.DIR
+            self.value = cosine
+            self.cosine = cosine
+
+    class Vec(SourceDefinitionOption):
+        """
+        ``Vec`` represents INP Vec source definition data card
+        options.
+
+        ``Vec`` inherits attributes from ``SourceDefinitionOption``. It
+        represents the INP Vec source definition data card option syntax element.
+
+        Attributes:
+            vector: Reference vector for DIR in vector notation.
+        """
+
+        def __init__(self, vector: tuple[types.McnpReal]):
+            """
+            ``__init__`` initializes ``Vec``.
+
+            Parameters:
+                vector: Reference vector for DIR in vector notation.
+
+            Raises:
+                MCNPSemanticError: INVALID_DATUM_SOURCE_VALUE.
+            """
+
+            if vector is None or not (len(vector) == 3):
+                raise errors.MCNPSemanticError(errors.MCNPSemanticCodes.INVALID_DATUM_SOURCE_VALUE)
+
+            x, y, z = vector
+
+            if x is None:
+                raise errors.MCNPSemanticError(errors.MCNPSemanticCodes.INVALID_DATUM_SOURCE_VALUE)
+
+            if y is None:
+                raise errors.MCNPSemanticError(errors.MCNPSemanticCodes.INVALID_DATUM_SOURCE_VALUE)
+
+            if z is None:
+                raise errors.MCNPSemanticError(errors.MCNPSemanticCodes.INVALID_DATUM_SOURCE_VALUE)
+
+            self.keyword = SourceDefinition.SourceDefinitionOption.SourceDefinitionKeyword.VEC
+            self.value = vector
+            self.vector = vector
+
+    class Nrm(SourceDefinitionOption):
+        """
+        ``Nrm`` represents INP Nrm source definition data card
+        options.
+
+        ``Nrm`` inherits attributes from ``SourceDefinitionOption``. It
+        represents the INP Nrm source definition data card option syntax element.
+
+        Attributes:
+            sign: Sign of the surface normal.
+        """
+
+        def __init__(self, sign: types.McnpInteger):
+            """
+            ``__init__`` initializes ``Nrm``.
+
+            Parameters:
+                sign: Sign of the surface normal.
+
+            Raises:
+                MCNPSemanticError: INVALID_DATUM_SOURCE_VALUE.
+            """
+
+            if sign is None:
+                raise errors.MCNPSemanticError(errors.MCNPSemanticCodes.INVALID_DATUM_SOURCE_VALUE)
+
+            self.keyword = SourceDefinition.SourceDefinitionOption.SourceDefinitionKeyword.NRM
+            self.value = sign
+            self.sign = sign
+
+    class Pos(SourceDefinitionOption):
+        """
+        ``Pos`` represents INP Pos source definition data card
+        options.
+
+        ``Pos`` inherits attributes from ``SourceDefinitionOption``. It
+        represents the INP Pos source definition data card option syntax element.
+
+        Attributes:
+            position: Reference point for sampling in vector notation.
+        """
+
+        def __init__(self, position: tuple[types.McnpInteger]):
+            """
+            ``__init__`` initializes ``Pos``.
+
+            Parameters:
+                position: Reference point for sampling in vector notation.
+
+            Raises:
+                MCNPSemanticError: INVALID_DATUM_SOURCE_VALUE.
+            """
+
+            if position is None or not (len(position) == 3):
+                raise errors.MCNPSemanticError(errors.MCNPSemanticCodes.INVALID_DATUM_SOURCE_VALUE)
+
+            x, y, z = position
+
+            if x is None:
+                raise errors.MCNPSemanticError(errors.MCNPSemanticCodes.INVALID_DATUM_SOURCE_VALUE)
+
+            if y is None:
+                raise errors.MCNPSemanticError(errors.MCNPSemanticCodes.INVALID_DATUM_SOURCE_VALUE)
+
+            if z is None:
+                raise errors.MCNPSemanticError(errors.MCNPSemanticCodes.INVALID_DATUM_SOURCE_VALUE)
+
+            self.keyword = SourceDefinition.SourceDefinitionOption.SourceDefinitionKeyword.POS
+            self.value = position
+            self.position = position
+
+    class Rad(SourceDefinitionOption):
+        """
+        ``Rad`` represents INP Rad source definition data card
+        options.
+
+        ``Rad`` inherits attributes from ``SourceDefinitionOption``. It
+        represents the INP Rad source definition data card option syntax element.
+
+        Attributes:
+            distance: Radial distance of the position.
+        """
+
+        def __init__(self, distance: Union[types.McnpReal, types.DistributionNumber]):
+            """
+            ``__init__`` initializes ``Rad``.
+
+            Parameters:
+                distance: Radial distance of the position.
+
+            Raises:
+                MCNPSemanticError: INVALID_DATUM_SOURCE_VALUE.
+            """
+
+            if distance is None:
+                raise errors.MCNPSemanticError(errors.MCNPSemanticCodes.INVALID_DATUM_SOURCE_VALUE)
+
+            self.keyword = SourceDefinition.SourceDefinitionOption.SourceDefinitionKeyword.RAD
+            self.value = distance
+            self.distance = distance
+
+    class Ext(SourceDefinitionOption):
+        """
+        ``Ext`` represents INP Ext source definition data card
+        options.
+
+        ``Ext`` inherits attributes from ``SourceDefinitionOption``. It
+        represents the INP Ext source definition data card option syntax element.
+
+        Attributes:
+             ext: Distance from POS along AXS or cosine of angle from AXS.
+        """
+
+        def __init__(self, ext: types.McnpReal):
+            """
+            ``__init__`` initializes ``Ext``.
+
+            Parameters:
+                ext: Distance from POS along AXS or cosine of angle from AXS.
+
+            Raises:
+                MCNPSemanticError: INVALID_DATUM_SOURCE_VALUE.
+            """
+
+            if ext is None:
+                raise errors.MCNPSemanticError(errors.MCNPSemanticCodes.INVALID_DATUM_SOURCE_VALUE)
+
+            self.keyword = SourceDefinition.SourceDefinitionOption.SourceDefinitionKeyword.EXT
+            self.value = ext
+            self.ext = ext
+
+    class Axs(SourceDefinitionOption):
+        """
+        ``Axs`` represents INP Axs source definition data card
+        options.
+
+        ``Axs`` inherits attributes from ``SourceDefinitionOption``. It
+        represents the INP Axs source definition data card option syntax element.
+
+        Attributes:
+            vector: Reference vector for EXT and READ.
+        """
+
+        def __init__(self, vector: tuple[types.McnpReal]):
+            """
+            ``__init__`` initializes ``Axs``.
+
+            Parameters:
+                vector: Reference vector for EXT and READ.
+
+            Raises:
+                MCNPSemanticError: INVALID_DATUM_SOURCE_VALUE.
+            """
+
+            if vector is None:
+                raise errors.MCNPSemanticError(errors.MCNPSemanticCodes.INVALID_DATUM_SOURCE_VALUE)
+
+            self.keyword = SourceDefinition.SourceDefinitionOption.SourceDefinitionKeyword.AXS
+            self.value = vector
+            self.vector = vector
+
+    class X(SourceDefinitionOption):
+        """
+        ``X`` represents INP X source definition data card
+        options.
+
+        ``X`` inherits attributes from ``SourceDefinitionOption``. It
+        represents the INP X source definition data card option syntax element.
+
+        Attributes:
+            x: X-coordinate of position.
+        """
+
+        def __init__(self, x: types.McnpReal):
+            """
+            ``__init__`` initializes ``X``.
+
+            Parameters:
+                x: X-coordinate of position.
+
+            Raises:
+                MCNPSemanticError: INVALID_DATUM_SOURCE_VALUE.
+            """
+
+            if x is None:
+                raise errors.MCNPSemanticError(errors.MCNPSemanticCodes.INVALID_DATUM_SOURCE_VALUE)
+
+            self.keyword = SourceDefinition.SourceDefinitionOption.SourceDefinitionKeyword.X
+            self.value = x
+            self.x = x
+
+    class Y(SourceDefinitionOption):
+        """
+        ``Y`` represents INP Y source definition data card
+        options.
+
+        ``Y`` inherits attributes from ``SourceDefinitionOption``. It
+        represents the INP Y source definition data card option syntax element.
+
+        Attributes:
+            y: Y-coordinate of position.
+        """
+
+        def __init__(self, y: types.McnpReal):
+            """
+            ``__init__`` initializes ``Y``.
+
+            Parameters:
+                y: Y-coordinate of position.
+
+            Raises:
+                MCNPSemanticError: INVALID_DATUM_SOURCE_VALUE.
+            """
+
+            if y is None:
+                raise errors.MCNPSemanticError(errors.MCNPSemanticCodes.INVALID_DATUM_SOURCE_VALUE)
+
+            self.keyword = SourceDefinition.SourceDefinitionOption.SourceDefinitionKeyword.Y
+            self.value = y
+            self.y = y
+
+    class Z(SourceDefinitionOption):
+        """
+        ``Z`` represents INP Z source definition data card
+        options.
+
+        ``Z`` inherits attributes from ``SourceDefinitionOption``. It
+        represents the INP Z source definition data card option syntax element.
+
+        Attributes:
+            z: Z-coordinate of position.
+        """
+
+        def __init__(self, z: types.McnpReal):
+            """
+            ``__init__`` initializes ``Z``.
+
+            Parameters:
+                y: Y-coordinate of position.
+
+            Raises:
+                MCNPSemanticError: INVALID_DATUM_SOURCE_VALUE.
+            """
+
+            if z is None:
+                raise errors.MCNPSemanticError(errors.MCNPSemanticCodes.INVALID_DATUM_SOURCE_VALUE)
+
+            self.keyword = SourceDefinition.SourceDefinitionOption.SourceDefinitionKeyword.Z
+            self.value = z
+            self.z = z
+
+    class Ccc(SourceDefinitionOption):
+        """
+        ``Ccc`` represents INP Ccc source definition data card
+        options.
+
+        ``Ccc`` inherits attributes from ``SourceDefinitionOption``. It
+        represents the INP Ccc source definition data card option syntax element.
+
+        Attributes:
+            number: Cookie-cutter cell number.
+        """
+
+        def __init__(self, number: types.McnpInteger):
+            """
+            ``__init__`` initializes ``Ccc``.
+
+            Parameters:
+                number Cookie-cutter cell number.
+
+            Raises:
+                MCNPSemanticError: INVALID_DATUM_SOURCE_VALUE.
+            """
+
+            if number is None:
+                raise errors.MCNPSemanticError(errors.MCNPSemanticCodes.INVALID_DATUM_SOURCE_VALUE)
+
+            self.keyword = SourceDefinition.SourceDefinitionOption.SourceDefinitionKeyword.CCC
+            self.value = number
+            self.number = number
+
+    class Ara(SourceDefinitionOption):
+        """
+        ``Ara`` represents INP Ara source definition data card
+        options.
+
+        ``Ara`` inherits attributes from ``SourceDefinitionOption``. It
+        represents the INP Ara source definition data card option syntax element.
+
+        Attributes:
+            area: Area of surface.
+        """
+
+        def __init__(self, area: types.McnpReal):
+            """
+            ``__init__`` initializes ``Ara``.
+
+            Parameters:
+                area: Area of surface.
+
+            Raises:
+                MCNPSemanticError: INVALID_DATUM_SOURCE_VALUE.
+            """
+
+            if area is None:
+                raise errors.MCNPSemanticError(errors.MCNPSemanticCodes.INVALID_DATUM_SOURCE_VALUE)
+
+            self.keyword = SourceDefinition.SourceDefinitionOption.SourceDefinitionKeyword.ARA
+            self.value = area
+            self.area = area
+
+    class Wgt(SourceDefinitionOption):
+        """
+        ``Wgt`` represents INP Wgt source definition data card
+        options.
+
+        ``Wgt`` inherits attributes from ``SourceDefinitionOption``. It
+        represents the INP Wgt source definition data card option syntax element.
+
+        Attributes:
+            weight: Particle weight.
+        """
+
+        def __init__(self, weight: types.McnpReal):
+            """
+            ``__init__`` initializes ``Wgt``.
+
+            Parameters:
+                weight: Particle weight.
+
+            Raises:
+                MCNPSemanticError: INVALID_DATUM_SOURCE_VALUE.
+            """
+
+            if weight is None:
+                raise errors.MCNPSemanticError(errors.MCNPSemanticCodes.INVALID_DATUM_SOURCE_VALUE)
+
+            self.keyword = SourceDefinition.SourceDefinitionOption.SourceDefinitionKeyword.WGT
+            self.value = weight
+            self.weight = weight
+
+    class Tr(SourceDefinitionOption):
+        """
+        ``Tr`` represents INP Tr source definition data card
+        options.
+
+        ``Tr`` inherits attributes from ``SourceDefinitionOption``. It
+        represents the INP Tr source definition data card option syntax element.
+
+        Attributes:
+            transformation: Source particle transformation number.
+        """
+
+        def __init__(self, transformation: types.McnpInteger):
+            """
+            ``__init__`` initializes ``Tr``.
+
+            Parameters:
+                transformation: Source particle transformation number.
+
+            Raises:
+                MCNPSemanticError: INVALID_DATUM_SOURCE_VALUE.
+            """
+
+            if transformation is None:
+                raise errors.MCNPSemanticError(errors.MCNPSemanticCodes.INVALID_DATUM_SOURCE_VALUE)
+
+            self.keyword = SourceDefinition.SourceDefinitionOption.SourceDefinitionKeyword.TR
+            self.value = transformatino
+            self.transformation = transformation
+
+    class Eff(SourceDefinitionOption):
+        """
+        ``Eff`` represents INP Eff source definition data card
+        options.
+
+        ``Eff`` inherits attributes from ``SourceDefinitionOption``. It
+        represents the INP Eff source definition data card option syntax element.
+
+        Attributes:
+            criterion: Rejection efficiency criterion for poition sampling.
+        """
+
+        def __init__(self, criterion: types.McnpReal):
+            """
+            ``__init__`` initializes ``Eff``.
+
+            Parameters:
+                criterion: Rejection efficiency criterion for poition sampling.
+
+            Raises:
+                MCNPSemanticError: INVALID_DATUM_SOURCE_VALUE.
+            """
+
+            if criterion is None:
+                raise errors.MCNPSemanticError(errors.MCNPSemanticCodes.INVALID_DATUM_SOURCE_VALUE)
+
+            self.keyword = SourceDefinition.SourceDefinitionOption.SourceDefinitionKeyword.EFF
+            self.value = criterion
+            self.criterion = criterion
+
+    class Par(SourceDefinitionOption):
+        """
+        ``Par`` represents INP Par source definition data card
+        options.
+
+        ``Par`` inherits attributes from ``SourceDefinitionOption``. It
+        represents the INP Par source definition data card option syntax element.
+
+        Attributes:
+            symbol: Source particle type by symbol or number.
+        """
+
+        def __init__(self, symbol: str):
+            """
+            ``__init__`` initializes ``Par``.
+
+            Parameters:
+                symbol: Source particle type by symbol or number.
+
+            Raises:
+                MCNPSemanticError: INVALID_DATUM_SOURCE_VALUE.
+            """
+
+            if symbol is None:
+                raise errors.MCNPSemanticError(errors.MCNPSemanticCodes.INVALID_DATUM_SOURCE_VALUE)
+
+            self.keyword = SourceDefinition.SourceDefinitionOption.SourceDefinitionKeyword.PAR
+            self.value = symbol
+            self.symbol = symbol
+
+    class Dat(SourceDefinitionOption):
+        """
+        ``Dat`` represents INP Dat source definition data card
+        options.
+
+        ``Dat`` inherits attributes from ``SourceDefinitionOption``. It
+        represents the INP Dat source definition data card option syntax element.
+
+        Attributes:
+            date: Date to use for cosmic-ray and background sources.
+        """
+
+        def __init__(self, date: tuple[types.McnpInteger]):
+            """
+            ``__init__`` initializes ``Dat``.
+
+            Parameters:
+                date: Date to use for cosmic-ray and background sources.
+
+            Raises:
+                MCNPSemanticError: INVALID_DATUM_SOURCE_VALUE.
+            """
+
+            if date is None or not (len(date) == 3):
+                raise errors.MCNPSemanticError(errors.MCNPSemanticCodes.INVALID_DATUM_SOURCE_VALUE)
+
+            m, d, y = date
+
+            if m is None or not (1 <= m <= 12):
+                raise errors.MCNPSemanticError(errors.MCNPSemanticCodes.INVALID_DATUM_SOURCE_VALUE)
+
+            if d is None or not (1 <= d <= 31):
+                raise errors.MCNPSemanticError(errors.MCNPSemanticCodes.INVALID_DATUM_SOURCE_VALUE)
+
+            if y is None or not (0 <= y <= 9999):
+                raise errors.MCNPSemanticError(errors.MCNPSemanticCodes.INVALID_DATUM_SOURCE_VALUE)
+
+            self.keyword = SourceDefinition.SourceDefinitionOption.SourceDefinitionKeyword.DAT
+            self.value = date
+            self.date = date
+
+    class Loc(SourceDefinitionOption):
+        """
+        ``Loc`` represents INP Loc source definition data card
+        options.
+
+        ``Loc`` inherits attributes from ``SourceDefinitionOption``. It
+        represents the INP Loc source definition data card option syntax element.
+
+        Attributes:
+            location: Location of cosmic particle source.
+        """
+
+        def __init__(self, location: tuple[types.McnpReal]):
+            """
+            ``__init__`` initializes ``Loc``.
+
+            Parameters:
+                location: Location of cosmic particle source.
+
+            Raises:
+                MCNPSemanticError: INVALID_DATUM_SOURCE_VALUE.
+            """
+
+            if location is None or not (len(location) == 3):
+                raise errors.MCNPSemanticError(errors.MCNPSemanticCodes.INVALID_DATUM_SOURCE_VALUE)
+
+            lat, lng, alt = location
+
+            if lat is None or not (-90 <= lat <= 90):
+                raise errors.MCNPSemanticError(errors.MCNPSemanticCodes.INVALID_DATUM_SOURCE_VALUE)
+
+            if lng is None or not (-180 <= lng <= 180):
+                raise errors.MCNPSemanticError(errors.MCNPSemanticCodes.INVALID_DATUM_SOURCE_VALUE)
+
+            if alt is None:
+                raise errors.MCNPSemanticError(errors.MCNPSemanticCodes.INVALID_DATUM_SOURCE_VALUE)
+
+            self.keyword = SourceDefinition.SourceDefinitionOption.SourceDefinitionKeyword.LOC
+            self.value = location
+            self.location = location
+
+    class Bem(SourceDefinitionOption):
+        """
+        ``Bem`` represents INP Bem source definition data card
+        options.
+
+        ``Bem`` inherits attributes from ``SourceDefinitionOption``. It
+        represents the INP Bem source definition data card option syntax element.
+
+        Attributes:
+            parameters: Beam emittance parameters.
+        """
+
+        def __init__(self, parameters: tuple[types.McnpReal]):
+            """
+            ``__init__`` initializes ``Bem``.
+
+            Parameters:
+                parameters: Beam emittance parameters.
+
+            Raises:
+                MCNPSemanticError: INVALID_DATUM_SOURCE_VALUE.
+            """
+
+            if parameters is None or not (len(parameters) == 3):
+                raise errors.MCNPSemanticError(errors.MCNPSemanticCodes.INVALID_DATUM_SOURCE_VALUE)
+
+            exn, eyn, bm1 = parameters
+
+            if exn is None:
+                raise errors.MCNPSemanticError(errors.MCNPSemanticCodes.INVALID_DATUM_SOURCE_VALUE)
+
+            if eyn is None:
+                raise errors.MCNPSemanticError(errors.MCNPSemanticCodes.INVALID_DATUM_SOURCE_VALUE)
+
+            if bm1 is None:
+                raise errors.MCNPSemanticError(errors.MCNPSemanticCodes.INVALID_DATUM_SOURCE_VALUE)
+
+            self.keyword = SourceDefinition.SourceDefinitionOption.SourceDefinitionKeyword.BEM
+            self.value = parameters
+            self.parameters = parameters
+
+    class Bap(SourceDefinitionOption):
+        """
+        ``Bap`` represents INP Bap source definition data card
+        options.
+
+        ``Bap`` inherits attributes from ``SourceDefinitionOption``. It
+        represents the INP Bap source definition data card option syntax element.
+
+        Attributes:
+            parameters: Beam aperture parameters.
+        """
+
+        def __init__(self, parameters: tuple[types.McnpReal]):
+            """
+            ``__init__`` initializes ``Bap``.
+
+            Parameters:
+                parameters: Beam aperture parameters.
+
+            Raises:
+                MCNPSemanticError: INVALID_DATUM_SOURCE_VALUE.
+            """
+
+            if parameters is None or not (len(parameters) == 3):
+                raise errors.MCNPSemanticError(errors.MCNPSemanticCodes.INVALID_DATUM_SOURCE_VALUE)
+
+            ba1, ba2, u = parameters
+
+            if ba1 is None or not (ba1 > 0):
+                raise errors.MCNPSemanticError(errors.MCNPSemanticCodes.INVALID_DATUM_SOURCE_VALUE)
+
+            if ba2 is None or not (ba2 > 0):
+                raise errors.MCNPSemanticError(errors.MCNPSemanticCodes.INVALID_DATUM_SOURCE_VALUE)
+
+            if u is None:
+                raise errors.MCNPSemanticError(errors.MCNPSemanticCodes.INVALID_DATUM_SOURCE_VALUE)
+
+            self.keyword = SourceDefinition.SourceDefinitionOption.SourceDefinitionKeyword.BAP
+            self.value = parameters
+            self.parameters = parameters
+
+    def __init__(self, pairs: tuple[SourceDefinitionOption]):
+        """
+        ``__init__`` initializes ``SourceDefinition``.
+
+        Parameters:
+            pairs: Tuple of key-value pairs.
+        """
+
+        if pairs is None:
+            raise errors.MCNPSemanticError(errors.MCNPSemanticCodes.INVALID_DATUM_PARAMETERS)
+
+        for pair in pairs:
+            if pair is None:
+                raise errors.MCNPSemanticError(errors.MCNPSemanticCodes.INVALID_DATUM_PARAMETERS)
+
+        self.id: final[str] = "sdef"
+        self.mnemonic: final[Datum.DatumMnemonic] = Datum.DatumMnemonic.GENERAL_SOURCE_DEFINITION
+        self.parameters: final[tuple] = pairs
+
+        self.pairs: final[SourceDefinitionOption] = pairs
+
+
 class HistroyCutoff(Datum):
     """
     ``HistroyCutoff`` represents INP nps data cards.