diff --git a/SC2166.md b/SC2166.md
index 03ea18f..04b2aee 100644
--- a/SC2166.md
+++ b/SC2166.md
@@ -1,4 +1,4 @@
-## Prefer `[ p ] && [ q ]` as `[ p -a q ]` is not well defined.
+## Prefer `[ p ] && [ q ]` as `[ p -a q ]` is not well-defined.
 
 And likewise, prefer `[ p ] || [ q ]` over `[ p -o q ]`.