Fin, fin clipping: median or paired structure, usually membranous and supported by soft rays or spines. Fins may be variously modified into other structures such as sucking discs or fishing poles.

Finless: without fins.

Finlet: small rayed fin structure behind dorsal and anal fins.

Finmark: leaving a distinguishable mark on the fin by removing a small part of the fin. This marking method (fin clipping) is used in studies of fish populations. These fin clip marks will disappear, usually within 1 or 2 years, because the fish have the capability to heal. See also finray, anal fin , and adipose fin. (figure types of dorsal fins), (figure internal organs).

Alternative forms for fin : fin clipping, finless, finlet, finmark.