diff --git a/src/derivatives/05-diffusion-derivatives.md b/src/derivatives/05-diffusion-derivatives.md
index a8df03be..c5625af5 100644
--- a/src/derivatives/05-diffusion-derivatives.md
+++ b/src/derivatives/05-diffusion-derivatives.md
@@ -856,7 +856,7 @@ Dictionary `"ResponseFunction"` has the following reserved keywords:
 
         for *maximum* spherical harmonic order *l<sub>max</sub>*.
 
-    -   Functions assumed to be real: conjugate symmetry is assumed, i.e.
+    -   Functions assumed to be real: conjugate symmetry is assumed, that is,
         *Y*(*l*,-*m*) = *Y*(*l*,*m*)\*, where \* denotes the complex
         conjugate.