diff --git a/STYLE_GUIDE.md b/STYLE_GUIDE.md
index 7ee0e2915..f3156a41f 100644
--- a/STYLE_GUIDE.md
+++ b/STYLE_GUIDE.md
@@ -82,3 +82,12 @@ MyAlgorithm(argOne, argTwo):
     - Let {something} be {true}.
 - Return {something}.
 ```
+
+## Definitions
+
+For important terms, use
+[Spec Markdown definition paragraphs](https://spec-md.com/#sec-Definition-Paragraph).
+
+Definition paragraphs start with `::` and add the matching italicized term to
+the [specification index](https://spec.graphql.org/draft/#index), making it easy
+to reference them.