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• fin
  fin

  noun

  a membranous, winglike or paddlelike organ attached to any of various parts of the body of fishes and certain other aquatic animals, used for propulsion, steering, or balancing.
• fin.
  fin.

  abbreviation

  finance.
• Fin.
  Fin.

  abbreviation

  Finland.
• FIN
  FIN

  abbreviation

  Finland (international car registration)
• Fin
  Fin

  abbreviation

  Finland

fin

¹ American  

[fin] / fɪn /

noun

1. a membranous, winglike or paddlelike organ attached to any of various parts of the body of fishes and certain other aquatic animals, used for propulsion, steering, or balancing.

2. Nautical.

   1. a horizontal, often adjustable, winglike appendage to the underwater portion of a hull, as one for controlling the dive of a submarine or for damping the roll of a surface vessel.

   2. fin keel.

3. Also called vertical stabilizer.  Aeronautics. any of certain small, subsidiary structures on an aircraft, designed to increase directional stability.

4. any of a number of standing ridges on an ordinarily hot object, as a radiator, a cylinder of an internal-combustion engine, etc., intended to maximize heat transfer to the surrounding air by exposing a large surface area.

5. any part, as of a mechanism, resembling a fin.

6. Metallurgy. a ridge of metal squeezed through the opening between two rolls, dies, or halves of a mold in which a piece is being formed under pressure.

7. Automotive. an ornamental structure resembling an aeronautical fin that is attached to the body of an automobile, as on each rear fender tail fin.

8. Slang. the arm or hand.

9. Usually fins. flipper.

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verb (used with object)

• fins,
  present (3rd person singular)
• finned,
  past participle,  past
• finning
  present participle

1. to cut off the fins from (a fish); carve or cut up, as a chub.

2. to provide or equip with a fin or fins.

verb (used without object)

• fins,
  present (3rd person singular)
• finned,
  past participle,  past
• finning
  present participle

1. to move the fins; lash the water with the fins, as a whale when dying.

fin ² American  

[fin] / fɪn /

noun

1. Slang. a five-dollar bill.

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fin. ³ American  

abbreviation

1. finance.

2. financial.

3. finish.

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Fin. ⁴ American  

abbreviation

1. Finland.

2. Finnish.

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FIN ¹ British  

abbreviation

1. Finland (international car registration)

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fin ² British  

/ fɪn /

noun

1. slang a five-dollar bill

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fin ³ British  

/ fɪn /

noun

1. any of the firm appendages that are the organs of locomotion and balance in fishes and some other aquatic animals. Most fishes have paired and unpaired fins, the former corresponding to the limbs of higher vertebrates

2. a part or appendage that resembles a fin

3. 1. US name: vertical stabilizer.  a vertical surface to which the rudder is attached, usually placed at the rear of an aeroplane to give stability about the vertical axis

   2. a tail surface fixed to a rocket or missile to give stability

4. nautical a fixed or adjustable blade projecting under water from the hull of a vessel to give it stability or control

5. a projecting rib to dissipate heat from the surface of an engine cylinder, motor casing, or radiator

6. (often plural) another name for flipper

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verb

1. (tr) to provide with fins

2. (tr) to remove the fins from (a dead fish)

3. (intr) (esp of a whale) to agitate the fins violently in the water

fin. ⁴ British  

abbreviation

1. finance

2. financial

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Fin ⁵ British  

abbreviation

1. Finland

2. Finnish

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fin Scientific  

/ fĭn /

1. One of the winglike or paddlelike parts of a fish, dolphin, or whale that are used for propelling, steering, and balancing in water.

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Other Word Forms

Derived Forms

• finless
  adjective
• finlike
  adjective

Inflected Forms

Participles

• finning
  present
• finned
  past

Conjugated Forms

Present

• fin
  simple
• fins
  simple
• have finned
  perfect
• has finned
  perfect
• am finning
  progressive
• are finning
  progressive
• is finning
  progressive
• have been finning
  perfect progressive
• has been finning
  perfect progressive

Past

• finned
  simple
• had finned
  perfect
• was finning
  progressive
• were finning
  progressive
• had been finning
  perfect progressive

Future

• will fin
  simple
• will have finned
  perfect
• will be finning
  progressive
• will have been finning
  perfect progressive

Etymology

Origin of fin¹

First recorded before 1000; Middle English, Old English finn; cognate with Dutch vin, Low German finne; akin to Swedish fena; probably akin to Latin pinna ( def. ); see also pen ¹ ( def. )

Origin of fin²

First recorded in 1865–70; earlier finnip, finnup, fin(n)if “a five-pound note,” from Yiddish fin(e)f “five,” from Middle High German vumf, vimf; see origin at five

Explanation

A fin is the part of a fish's body that protrudes into the water and helps it balance and move in various directions. Sharks use their dorsal fins to stabilize their bodies as they propel through the water. Fish, whales, dolphins, and other aquatic animals have fins on various parts of their bodies. Surfboards often have a rear fin that works in a similar way, helping to keep the board steady and aid in making turns. Ships, cars, and aircraft also have fins that assist with balance. In Old English, it was finn, which probably comes from the Latin pinna, "feather or wing."

Example Sentences

See Examples For:

fin fin. Fin. FIN Fin fins finned finning

This isn’t the only thing going on this summer that gives me that ominous fin de siècle feeling.

From MarketWatch ● Aug. 12, 2026

The project also included Duke University plastic surgeon David A. Brown, who studies digit regeneration in mice, and Kenneth D. Poss of the University of Wisconsin-Madison, whose research focuses on fin regeneration in zebrafish.

From Science Daily ● May 9, 2026

Tide tables have become the stuff of national interest, and rare moments when the exhausted whale has blown water or flapped its fin have warranted breaking news bulletins.

From Barron's ● Apr. 23, 2026

The catalog begins with fin de siècle Europe, when the emergence of mass publishing began to lead to a firmer distinction between subordinate illustrators and visionary fine artists.

From The Wall Street Journal ● Nov. 21, 2025

This time, she was in a group of people, standing at the water’s edge, looking at a dorsal fin poking out from the flat calm.

From "The Line Tender" by Kate Allen

After long observation and many trials they decided that fin. strips of metal screening tacked to the ceiling are what flies like best.

From Time Magazine Archive

“That’s when I lost part of my tail and cracked my fin. Not a big deal when I’m in fish form, but it’s a bit inconvenient here at Sea Bottom.”

From "When the Sea Turned to Silver" by Grace Lin

“Look at the fin. Floppy on top. It’s not a shark.”

From "Shouting at the Rain" by Lynda Mullaly Hunt

IV, 12, ad fin., note, for the statement that he was “Bishop” of Ripon.498.King of Northumbria, v.s. c.

From Bede's Ecclesiastical History of England by Cuthbert Bede

II, 5 ad fin., note.316.Cf. note on Cuichelm, II, 9.

From Bede's Ecclesiastical History of England by Cuthbert Bede

Moss and Njemile were getting off at the MacArthur station the next morning when Njemile said, “I declare this year over. Fin. Cerrado. Done.”

From "Anger Is a Gift" by Mark Oshiro

Translations from Greek poets occur in the philosophical works, e.g. de Fin. v.

From The Student's Companion to Latin Authors by George Middleton

At the same time he is not a mere translator: de Fin. i.

From The Student's Companion to Latin Authors by George Middleton

Fin. i. 16, like ὠφέλημα; whereas quæstus and compendium denote gain in the course of trade; quæstus, rather the steadily continued gains of a regular occupation, earnings, in opp. to sumptus; Cic.

From Döderlein's Hand-book of Latin Synonymes by Ludwig Döderlein

In the Hortensius Cicero appeared as the champion of philosophy: De Fin. i.

From The Student's Companion to Latin Authors by George Middleton

“We figured out a day before we started shooting that these things don’t quite marry up,” said Johnstone, who turned to FIN Design and Effects of Australia to blend his M3GANs together.

From Los Angeles Times ● Jan. 7, 2023

USA 1-0 FIN 20:00 That’s the end of the period — the goal from defenseman Faulk, a Carolina prospect who now plays for Minnesota-Duluth, is all the scoring in a relatively tame opening stanza.

From New York Times ● Dec. 27, 2010

USA 3-2 FIN … two points for the Amerks, one for the Finns.

From New York Times ● Dec. 27, 2010

In fact, "Breathless" is dedicated to Monogram Pictures, an American studio that specialized in grade-B crime dramas, and carries no other credits: only the title at the beginning and the word "FIN" at the end.

From Salon ● May 29, 2010

They may be distinguished from sei whales in the following similar ways: Fin WhaleSei WhaleDORSAL FIN Slightly falcate, forms angle of less than 40° with back slightly more than one-third forward from tail.

From Whales, Dolphins, and Porpoises of the Western North Atlantic A Guide to Their Identification by David Caldwell

They said it could rise even higher if Salesforce’s acquisitions of Contentful and Fin close in the upcoming weeks.

From MarketWatch ● Aug. 27, 2026

Fin Monahan said South Wales Fire and Rescue Service was under severe pressure and very grateful to seven other fire services and the military for help.

From BBC ● Aug. 16, 2026

Boro boss Kim Hellberg urged Lankshear to hurry up, but he took too long and substitute Fin Cartwright was told he could not come on immediately.

From BBC ● Aug. 14, 2026

Intercom, a 15-year-old customer-service software business, built an AI customer-service agent called Fin.

From The Wall Street Journal ● Aug. 7, 2026

He and the Fin Chaser owner were really tight until Mom got sick and Dad quit working.

From "The Young Man and the Sea" by Rodman Philbrick

Munich's Allianz Arena is sculpted by thousands of diamond-shaped inflatable cushions, while Sydney's similarly-named Allianz Stadium has a flatter façade smoothed with long bronze fins.

From BBC ● Aug. 22, 2026

The shark made a few circles, its fins at times breaching the water’s surface as stunned fishermen looked on.

From Los Angeles Times ● Aug. 15, 2026

The hapless sunfish can weigh up to 2,000 kilograms and is distinct for both its size and peculiar shape featuring a flattened body and fins.

From Barron's ● Jul. 23, 2026

The drum of an arena would be surrounded by an elegant rectangular box with vertical fins and tall windows.

From The Wall Street Journal ● Jun. 13, 2026

There was a smudge of soot there, spreading up onto the fins.

From "October Sky" by Homer Hickam

The first lobe finned fish that developed limbs capable of supporting movement on land still relied heavily on aquatic environments.

From Science Daily ● Feb. 11, 2026

Magnus wrote in his 1555 book they were 200-feet long with broad, forked tails and finned feet, with faces resembling warthogs and dual blow-holes on the top of their heads.

From National Geographic ● Dec. 28, 2023

Large finned automobiles that resemble 1950s classics hover over smooth roads, as do baby carriages across perfectly clean sidewalks in perfectly manicured suburbs.

From Los Angeles Times ● Feb. 17, 2023

Print off the wildlife checklist before you go and watch for a Pacific jumping mouse and Roosevelt elk, among hundreds of finned, furred and feathered creatures listed.

From Seattle Times ● Jul. 21, 2021

He could feel the rumble of the craft’s engines tilling the air but couldn’t make out the silver skin, the sweeping ribs, the finned tail.

From "Unbroken" by Laura Hillenbrand

What’s more, illegal finning for export to Asia still remains a major concern in Brazil, with Brazilian authorities reporting in late June that they’d seized an enormous haul of illegally obtained shark fins.

From National Geographic ● Jul. 17, 2023

The practice of shark finning, whereby sharks are caught for their fins and their carcasses then dumped back into the ocean, has been banned in U.S. waters for decades.

From Seattle Times ● Dec. 16, 2022

And finning is already illegal in U.S. waters.

From Washington Post ● Dec. 15, 2022

“Roger wanted to know how many species were being overfished, how many sharks were being killed for finning, and whether Sea Shepherd’s efforts were affecting these numbers,” he says.

From Science Magazine ● Jun. 30, 2022

The sale had not long been concluded, and the little community were preparing to obey Acton's order to "Come outside," when the latter rushed into the room finning with rage.

From The Triple Alliance Its trials and triumphs by Harold Avery