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• key
  key

  noun

  a small metal instrument specially cut to fit into a lock and move its bolt.
• Key
  Key

  noun

  Francis Scott, 1780–1843, U.S. lawyer: author of The Star-Spangled Banner.

key

¹ American  

[kee] / ki /

noun

• keys
  plural

1. a small metal instrument specially cut to fit into a lock and move its bolt.

2. any of various devices resembling or functioning as a key.

   the key of a clock.

3. key card.

4. something that affords a means of access.

   the key to happiness.

5. something that secures or controls entrance to a place.

   Gibraltar is the key to the Mediterranean.

6. something that affords a means of clarifying a problem.

   Synonyms:

   pivotal, major, chief, clue, resolution, explanation, answer

7. a book, pamphlet, or other text containing the solutions or translations of material given elsewhere, as testing exercises.

8. a systematic explanation of abbreviations, symbols, etc., used in a dictionary, map, etc..

   pronunciation key.

9. the system, method, pattern, etc., used to decode or decipher a cryptogram, as a code book, machine setting, or keyword.

10. one of a set of marked parts, designated areas, or levers pressed in operating a typewriter, computer terminal, calculator, etc.

11. a manually operated lever for opening and closing an electric circuit, used to produce signals in telegraphy.

12. Music.

    1. (in a keyboard instrument) one of the levers that when depressed by the performer sets in motion the playing mechanism.

    2. (on a woodwind instrument) a metal lever that opens and closes a vent.

    3. the relationship perceived between all tones in a given unit of music and a single tone or a keynote; tonality.

    4. the principal tonality of a composition.

       a symphony in the key of C minor.

    5. the keynote or tonic of a scale.

13. tone or pitch, as of voice.

    to speak in a high key.

14. mood or characteristic style, as of expression or thought.

    He writes in a melancholy key.

15. degree of intensity, as of feeling or action.

16. a pin, bolt, wedge, or other piece inserted in a hole or space to lock or hold parts of a mechanism or structure together; a cotter.

17. a small piece of steel fitting into matching slots of a hub of a wheel or the like and the shaft on which the wheel is mounted so that torque is transmitted from one to the other.

18. a contrivance for grasping and turning a bolt, nut, etc.

19. Computers. a field or group of characters within a record that identifies the record, establishing its position among sorted records, and/or provides information about its contents.

20. (in a series of advertisements or announcements soliciting replies) a unique code inserted for each medium used, to determine the relative effectiveness of the media.

21. Electricity.

    1. a device for opening and closing electrical contacts.

    2. a hand-operated switching device ordinarily formed of concealed spring contacts with an exposed handle or push button, capable of switching one or more parts of a circuit.

22. Biology. a systematic tabular classification of the significant characteristics of the members of a group of organisms to facilitate identification and comparison.

23. Masonry. a keystone.

24. Architecture. (in a ribbed vault) a stone, as a boss, at the intersection of two or more ribs.

25. Masonry, Carpentry. a wedge, as for tightening a joint or splitting a stone or timber.

26. Carpentry. a small piece of wood set into a timber across the grain to prevent warping.

27. Building Trades. any grooving or roughness applied to a surface to improve its bond with another surface.

28. Basketball. keyhole.

29. Photography. the dominant tonal value of a picture, a high-key picture having light tonal values and minimal contrast and a low-key picture being generally dark with minimal contrast.

30. Painting. the tonal value and intensity of a color or range of colors.

    Rembrandt's colors are characterized by their low key.

31. Botany. a samara.

32. Key, a member of the House of Keys.

33. keys, spiritual authority.

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adjective

1. essential; central; important.

   a key person in the company;

   key industries.

verb (used with object)

• keys,
  present (3rd person singular)
• keyed,
  past participle,  past
• keying
  present participle

1. to regulate or adjust (actions, thoughts, speech, etc.) to a particular state or activity; bring into conformity.

   to key one's speech to the intellectual level of the audience.

2. Music. to regulate the key or pitch of.

3. Painting.

   1. to paint (a picture) in a given key.

   2. to adjust the colors in (a painting) to a particular hue.

      He keyed the painting to brown.

4. to fasten, secure, or adjust with a key, wedge, or the like, as parts of a mechanism.

5. to provide with a key.

6. (in the layout of newspapers, magazines, etc.) to identify, through signs or symbols, the positions of illustrations or pieces of copy in a dummy.

7. to lock with or as if with a key.

8. Masonry. to provide (an arch or vault) with a keystone.

9. Computers. keyboard.

verb (used without object)

• keys,
  present (3rd person singular)
• keyed,
  past participle,  past
• keying
  present participle

1. to use a key.

2. Computers. keyboard.

verb phrase

1. key on

   1. Football. to watch the position and movements of an opponent in order to anticipate a play.

      The defensive backs keyed on the star receiver.

   2. Also key in on to single out as of prime importance or interest; be intent on or obsessed with.

      a company that is keyed in on growth.

2. key in keyboard.

3. key up

   1. to bring to a particular degree of intensity of feeling, excitement, energy, nervousness, agitation, etc..

      keyed up over the impending test.

   2. to raise (a piece of masonry) by the insertion of a wedge or wedges.

   3. to raise (the haunches of an arch) by the insertion of a voussoir.

idioms

1. power of the keys, the authority of a pope in ecclesiastical matters, vested in him as successor of St. Peter.

key ² American  

[kee] / ki /

noun

• keys
  plural

1. a reef or low island; cay.

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key ³ American  

[kee] / ki /

noun

Slang.

• keys
  plural

1. a kilogram of marijuana or other narcotic drug.

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Key ⁴ American  

[kee] / ki /

noun

1. Francis Scott, 1780–1843, U.S. lawyer: author of The Star-Spangled Banner.

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key ¹ British  

/ kiː /

noun

1. a variant spelling of cay

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key ² British  

/ kiː /

noun

1. a metal instrument, usually of a specifically contoured shape, that is made to fit a lock and, when rotated, operates the lock's mechanism

2. any instrument that is rotated to operate a valve, clock winding mechanism, etc

3. a small metal peg or wedge inserted into keyways

4. any of a set of levers operating a typewriter, computer, etc

5. any of the visible parts of the lever mechanism of a musical keyboard instrument that when depressed set in motion the action that causes the instrument to sound

6. 1. Also called: tonality. any of the 24 major and minor diatonic scales considered as a corpus of notes upon which a piece of music draws for its tonal framework

   2. the main tonal centre in an extended composition

      a symphony in the key of F major

   3. the tonic of a major or minor scale

   4. See tuning key

7. something that is crucial in providing an explanation or interpretation

   the key to adult behaviour lies in childhood

8. a means of achieving a desired end

   the key to happiness

9. a means of access or control

   Gibraltar is the key to the Mediterranean

10. a list of explanations of symbols, codes, etc

11. a text that explains or gives information about a work of literature, art, or music

12. Also called: key move. the correct initial move in the solution of a set problem

13. biology a systematic list of taxonomic characteristics, used to identify animals or plants

14. photog painting the dominant tonal value and colour intensity of a picture See also low-key high-key

15. electrical engineering

    1. a hand-operated device for opening or closing a circuit or for switching circuits

    2. a hand-operated switch that is pressed to transmit coded signals, esp Morse code

16. the grooving or scratching of a surface or the application of a rough coat of plaster, etc, to provide a bond for a subsequent finish

17. pitch

    he spoke in a low key

18. a characteristic mood or style

    a poem in a melancholic key

19. level of intensity

    she worked herself up to a high key

20. railways a wooden wedge placed between a rail and a chair to keep the rail firmly in place

21. a wedge for tightening a joint or for splitting stone or timber

22. short for keystone

23. botany any dry winged fruit, esp that of the ash

24. (modifier) photog determining the tonal value of a photograph

    flesh colour is an important key tone

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adjective

1. of great importance; crucial

   a key issue

verb

1. (foll by to) to harmonize (with)

   to key one's actions to the prevailing mood

2. to adjust or fasten with a key or some similar device

3. to provide with a key or keys

4. to scratch the paintwork of (a car) with a key

5. (often foll by up) to locate the position of (a piece of copy, artwork, etc) on a layout by the use of symbols

6. (also intr) another word for keyboard

7. to include a distinguishing device in (an advertisement, etc), so that responses to it can be identified

8. to provide a keystone for (an arch)

Key ³ British  

/ kiː /

noun

1. John ( Phillip ). born 1961, New Zealand politician; prime minister from 2008

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key Scientific  

/ kē /

1. See cay

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key Cultural  

1. The main or central note of a piece of music (or part of a piece of music). Each key has its own scale, beginning and ending on the note that defines the octave of the next scale. The key of C-major uses a scale that starts on C and uses only the white keys of the piano. In a piece composed in the key of C, the music is likely to end on the note C, and certain combinations of notes based on C will predominate.

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key More Idioms  

More idioms and phrases containing key

• in key
• under lock and key

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Other Word Forms

Derived Forms

• keyless
  adjective

Inflected Forms

Nouns

• keys
  plural

Participles

• keying
  present
• keyed
  past

Conjugated Forms

Present

• key
  simple
• keys
  simple
• have keyed
  perfect
• has keyed
  perfect
• am keying
  progressive
• are keying
  progressive
• is keying
  progressive
• have been keying
  perfect progressive
• has been keying
  perfect progressive

Past

• keyed
  simple
• had keyed
  perfect
• was keying
  progressive
• were keying
  progressive
• had been keying
  perfect progressive

Future

• will key
  simple
• will have keyed
  perfect
• will be keying
  progressive
• will have been keying
  perfect progressive

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Etymology

Origin of key¹

First recorded before 900; Middle English key(e), kay(e), Old English cǣg, cǣge; cognate with Old Frisian kei, kai

Origin of key²

First recorded in 1690–1700; from Spanish cayo, probably from Arawak

Origin of key³

An Americanism dating back to 1965–70; shortening and respelling of kilogram

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Explanation

A key is a piece of metal that fits inside a lock and turns to open it. You might have a key ring with a house key, a car key, and maybe several more keys. A key is typically cut from metal, although many hotels use plastic keys for their guest rooms. If you are told that your attendance is key, you know you have to go. Another meaning of key is a button or lever you press with your fingers, like a piano key or a typewriter key. A key is also an explanation, like the answer key for a test or the key to success. And when you sing in key, you have the correct pitch.

Example Sentences

See Examples For:

key Key keys keyed keying

The liver may hold an unexpected key to fighting two of the most serious diseases associated with aging: Alzheimer's disease and heart disease.

From Science Daily ● Nov. 3, 2026

Fifa says "key documents" relating to president Gianni Infantino's failed plan to sell off stakes in the World Cup to private investors will be made available to members of its council.

From BBC ● Nov. 2, 2026

Investors are watching races in key states for pushback against the AI infrastructure build-out.

From The Wall Street Journal ● Nov. 2, 2026

Meta CEO Mark Zuckerberg, Instagram chief Adam Mosseri and Snap CEO Evan Spiegel had been expected to be called as key witnesses in the upcoming Los Angeles trial.

From Barron's ● Nov. 2, 2026

I shove the letter back in the chest, put the padlock on it and zip the key into my pocket.

From "Code Name Kingfisher" by Liz Kessler

To celebrate his recovery, Dave is planning a 110-mile bicycle ride from Miami to Key West in March 2027.

From The Wall Street Journal ● Nov. 1, 2026

Key details: The so-called core PCE index rose a slower but still worrisome 0.3% in September, matched the forecast of economists surveyed by The Wall Street Journal.

From MarketWatch ● Oct. 29, 2026

Key aspects of the plan differ from the Trump administration’s public pronouncements.

From Salon ● Oct. 23, 2026

Key signs can be "checking" behaviours, such as frequently examining your body, taking your temperature, blood pressure or researching symptoms online.

From BBC ● Oct. 22, 2026

The neighborhood of Key West where the cigar factories were located was called Gatoville.

From Full of Beans by Jennifer L. Holm

Guests at his property in south-west London are asked only to lock up and return the keys.

From BBC ● Nov. 1, 2026

One of the keys to understanding the foveola is a group of specialized light-detecting cells called cones.

From Science Daily ● Oct. 31, 2026

I have a very specific fantasy about the restaurant I would open, should someone ever hand me a set of keys and an unlimited supply of funds and optimism.

From Salon ● Oct. 30, 2026

Then, in 2025, she has decided to hand over the keys to a new owner in a move she described as “bittersweet.”

From MarketWatch ● Oct. 30, 2026

Of course, I’d watched Dad spend an hour looking for car keys that were in his pocket, but still.

From "Klawde: Evil Alien Warlord Cat" by Johnny Marciano and Emily Chenoweth

For investors, there are many ways to play commodities, including exchange-traded funds keyed off agricultural commodities and food-related stocks.

From Barron's ● Sep. 4, 2026

Health officials have keyed in on iceberg lettuce as a potential source.

From MarketWatch ● Aug. 18, 2026

The emotional tone of each vocal performance is beautifully keyed to each song’s context.

From Salon ● Jul. 14, 2026

Granada Hills 4, El Camino Real 3: A two-run single by Nicholas Penaranda in the seventh inning keyed a three-run inning for the Highlanders in their West Valley League upset.

From Los Angeles Times ● Mar. 26, 2026

I snuck by easy, keyed open the office door with the long key and quietly pulled it shut behind me.

From "We Were Here" by Matt De La Peña

In an interview with Axios published Sunday, Trump said “We are low keying it” with Iran.

From MarketWatch ● Aug. 9, 2026

“When the market is keying off fundamentals, around earnings season of these companies, these stocks rally,” Slimmon said.

From The Wall Street Journal ● Dec. 18, 2025

Once again, the internet flooded with Black Flag memes keying on the considerable age gap between Ginn, who is 70, and his new bandmates who look many decades, if not generations, younger.

From Los Angeles Times ● May 29, 2025

In the nearby city of San José, a man was arrested March 17 for allegedly keying a Tesla parked in a Costco lot.

From Los Angeles Times ● Apr. 1, 2025

He consulted his notes, keying in on one thing in particular.

From "The Last Last-Day-of-Summer" by Lamar Giles

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