Intermediate+ Word of the Day: fin

fin (noun, verb) /fɪn/ LISTEN

A fin is the wing-like part of the body of fishes and water mammals such as whales used for moving, steering, and balancing. Any part that resembles this is also called a fin, like the ones aircraft or boats have. Fins, usually in the plural, are the rubber devices that some swimmers or divers use on their feet when swimming underwater. As a verb, fin is not common, but when it is used, it means ‘to move using fins’ or ‘to equip with fins,’ as is done with boats or aircraft, or, if we are talking about a fish, ‘to remove the fins from.’

Example sentences

  • With a flick of its fins, the fish swam away.
  • The aircraft's fins provide stability.
  • The diver put on her fins.
  • The fish finned through the water.
  • The ship had been finned and was ready to sail.
  • The fishmonger finned the fish.

Additional information

A fin is also a colloquial word for a five dollar bill. Example: “I’m short of cash. Can you lend me a fin?”

In pop culture

The movie Finding Nemo is about a young clownfish who has one fin that is much smaller than the other. In this scene from the movie, you can see Nemo’s first day at school and the other kids asking him about his little fin:

Did you know?

-fin- is also found as a component of other words. It comes from Latin, where it means ‘end’, as in the words finish, final, or finale, or ‘limit’, as in the words define, confine, or finite.

Commonly confused with

Don’t confuse fin with Finn. A Finn is a person from Finland.


Fin dates back to before the year 1000. The Old and Middle English noun finn came from the Proto-Germanic finna, which, most linguists believe, can be traced back to the Latin noun pinna, meaning ‘a feather’ as well as ‘a fin,’ and the Proto-Indo-European root pet- (to rush or fly). A few linguists, however, propose a different origin: the Latin noun spina (thorn or spine), from the Proto-Indo-European root spei- (sharp point). In either case, fin is related to the Low German finne, the Middle Low German vinne and the Dutch vin, as well as the Swedish fena (all meaningfin). If the noun’s origin is the Latin pinna, it is also related to the English words pen and pin, among others. If its origin is the Latin noun spina, it is related to the English words spine and spike. The verb comes from the noun, and has been used (though rarely) since the late 14th century. The colloquial use of the word fin to mean ‘a five dollar bill’ dates back to the 1920s, and comes from the Yiddish (Jewish German dialect) word finif, from the German fünf (five).

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