- "Mode enabling subword movement and editing keys.
-In spite of GNU Coding Standards, it is popular to name a symbol by
-mixing uppercase and lowercase letters, e.g. \"GtkWidget\",
-\"EmacsFrameClass\", \"NSGraphicsContext\", etc. Here we call these
-mixed case symbols `nomenclatures'. Also, each capitalized (or
-completely uppercase) part of a nomenclature is called a `subword'.
-Here are some examples:
+ "Toggle subword movement and editing (Subword mode).
+With a prefix argument ARG, enable Subword mode if ARG is
+positive, and disable it otherwise. If called from Lisp, enable
+the mode if ARG is omitted or nil.
+
+Subword mode is a buffer-local minor mode. Enabling it remaps
+word-based editing commands to subword-based commands that handle
+symbols with mixed uppercase and lowercase letters,
+e.g. \"GtkWidget\", \"EmacsFrameClass\", \"NSGraphicsContext\".
+
+Here we call these mixed case symbols `nomenclatures'. Each
+capitalized (or completely uppercase) part of a nomenclature is
+called a `subword'. Here are some examples: