diff --git a/usr.bin/sed/sed.1 b/usr.bin/sed/sed.1
--- a/usr.bin/sed/sed.1
+++ b/usr.bin/sed/sed.1
@@ -431,7 +431,9 @@
 preceding backslash) for each byte in the character (most significant byte
 first).
 Long lines are folded, with the point of folding indicated by displaying
-a backslash followed by a newline.
+a backslash followed by a newline. The point of folding is controlled by
+the size of the terminal or by explicitly setting
+.Ev COLUMNS .
 The end of each line is marked with a
 .Dq $ .
 .Pp