ANSI Common Lisp   2 Syntax   2.4 Standard Macro Characters

2.4.4 Semicolon

Syntax: ;<<text>>

A semicolon introduces characters that are to be ignored, such as comments. The semicolon and all characters up to and including the next newline or end of file are ignored.

2.4.4.1  Examples of Semicolon
2.4.4.2  Notes about Style for Semicolon