Fin, fins: 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 but this does not refer to Osteoglossomorpha.
(Measurements 1 ) Fins in bony fishes usually serve as a means of communication. Displaying or hiding e. g. in mating behaviour signalises the mate or a rival the mood of the owner of a spawning site.

Alternative form for fin : fins.