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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. finance

2. financial

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fin ² British  

/ fɪn /

noun

1. slang a five-dollar bill

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FIN ³ British  

abbreviation

1. Finland (international car registration)

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fin ⁴ 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 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

Known as The Flying Kangaroo for the logo displayed on its tail fin and elsewhere, Qantas is investing heavily in fleet renewal that could help it better mitigate the impact of future fuel-price shocks.

From The Wall Street Journal ● Aug. 27, 2026

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

She had asked plenty of questions when the scope of her work had extended only from the nose cone of a tiny Cessna 405 to its tail fin.

From "Hidden Figures" by Margot Lee Shetterly

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

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

From "Shouting at the Rain" by Lynda Mullaly Hunt

“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

III, 3, ad fin., note.558.Innisboffin, off the coast of Mayo.

From Bede's Ecclesiastical History of England by Cuthbert Bede

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

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

Fin. iv. 14; defendere, an actual 215 attack, as to defend, in opp. to deserere.

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

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

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

I have often indeed heard the saying, On peut etre plus FIN qu'un autre, mais pas plus FIN que tous les autres.

From Life of John Sterling by Thomas Carlyle

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

Britain's Fin Tarling, 19, died during the Volta a Portugal on Friday following a high-speed collision with a van which had strayed on to the closed road.

From BBC ● Aug. 18, 2026

Fin Tarling himself had finished strongly in the time trial a few days earlier in the race he would never finish.

From BBC ● Aug. 15, 2026

It reached $400 million in annual recurring revenue earlier this year, and Salesforce agreed in June to acquire Fin for $3.6 billion.

From The Wall Street Journal ● Aug. 7, 2026

Fin was seated on a stool at her workbench, mending a gardening tool.

From "Huntress" by Malinda Lo

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

More high-quality footage is needed, particularly clear views of dorsal fins and eye patches, which can be used to identify individual animals.

From Science Daily ● Jul. 23, 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

Matthews said the device actually contained "a load of cardboard fins that get wet as the water blows past them".

From BBC ● Jul. 10, 2026

My teammates are all here, dressed in outfits of bright white with flippers on our feet and fins on our arms.

From "Warcross" by Marie Lu

The finned culprit “nipped” at the unidentified 54-year-old swimmer, causing non-life-threatening injuries to the man’s leg and foot, according to Los Angeles Fire Department Capt. Adam VanGerpen.

From Los Angeles Times ● Sep. 30, 2025

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

Extra-long rear flippers might have aided propulsion in concert with its long finned tail.

From Science Daily ● Dec. 12, 2023

State media released a photo of a missile mounted with a finned, cone-shaped payload soaring into the air while leaving a trial of bright orange flames.

From Seattle Times ● Sep. 28, 2021

The little fish leaped from the water to show the smooth shine of their finned tails and the rabbits turned their rumps so the Terrible Things could see for themselves.

From "Terrible Things: An Allegory of the Holocaust" by Eve Bunting

Some also suggested that, ironically, finning bans may have contributed to the rise in shark mortality.

From Science Magazine ● Jan. 10, 2024

But that’s changed: A growing number of finning prohibitions in recent decades have made slicing and dumping illegal in more than 90 percent of the world’s oceans.

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

In reality, the top threat to sharks and their relatives, by far, is unsustainable overfishing, which includes, but is not limited to, shark finning.

From Scientific American ● May 24, 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