5. Comments

Single-line comments start with a semicolon (;):

;; This is a single-line comment
(+ 2 3) ; This is also a comment

If they start the line, by convention two semicolons (;;) are used. Whereas if you are leaving a clarification, a single semicolon (;) is used at the end of the line.

Multi-line comments start with #| and end with |#:

#|
    This is a
    multi-line comment
|#

In addition, block comments can have nested levels:

#|
    This is the main
    multi-line comment
    #|
        This is a nested comment
    |#
    This is the continuation of the main comment
|#