Forth supports two styles of comment; the traditional in-line comment, ( and its modern cousin, the comment to end of line; \.

( ( compilation ’ccc<close-paren>’ – ; run-time –  ) core,file “paren”

Comment, usually till the next ): parse and discard all subsequent characters in the parse area until ")" is encountered. During interactive input, an end-of-line also acts as a comment terminator. For file input, it does not; if the end-of-file is encountered whilst parsing for the ")" delimiter, Gforth will generate a warning.

\ ( compilation ’ccc<newline>’ – ; run-time –  ) core-ext,block-ext “backslash”

Comment until the end of line: parse and discard all remaining characters in the parse area, except while loading from a block: while loading from a block, parse and discard all remaining characters in the 64-byte line.

\G ( compilation ’ccc<newline>’ – ; run-time –  ) gforth-0.2 “backslash-gee”

Equivalent to \ but used as a tag to annotate definition comments into documentation.