diff --git a/usr.bin/grep/grep.1 b/usr.bin/grep/grep.1
index 38f96396f27..1db95169d0a 100644
--- a/usr.bin/grep/grep.1
+++ b/usr.bin/grep/grep.1
@@ -300,7 +300,7 @@ Use
 instead of
 .Xr read 2
 to read input, which can result in better performance under some
-circumstances but can cause undefined behaiour.
+circumstances but can cause undefined behaviour.
 .It Fl m Ar num, Fl Fl max-count Ns = Ns Ar num
 Stop reading the file after
 .Ar num