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key definition


This page has 53 definitions of key in English, Central Kurdish, and Manx. Key is a noun, an adjective, verb and adverb. Examples of how to use key in a sentence are shown. Also define these 109 related words and terms: lock, shaft, wheel, orientation, crucial, legend, worksheet, computing, text, character, music, instrument, valve, lever, hole, woodwind, keyboard, organ, piano, keynote, melodic, harmonic, scale, tonality, notation, staff, advertising, group, demographic, botany, indehiscent, fruit, wing, ash, maple, samara, electrical, switch, Morse code, cryptography, passphrase, encode, decode, Internet, password, IRC, channel, database, relational database, field, index, table, unique, container, basketball, skeleton key, biology, logical, organize, discriminate, identify, taxon, architecture, masonry, keystone, plastering, lath, rail transport, rail, bullhead rail, roughness, retention, cartomancy, Lenormand, black, ink, CMYK, computer graphics, television, color, mask, transparent, indispensable, important, salient, mark, indicate, symbol, membership, class, telegraphy, radio telegraphy, radio, enter, keypad, vandalize, scratch, link, taxonomy, identified, attune, pitch, island, quay, kilogram, kay, when, cream, and nautical.

See also: Key

English key definition

A key (object designed to open and close a lock)
A numeric keypad with 16 keys
The keys of a musical keyboard.
The key of a map.
A telegraph key


Etymology 1

From Middle English keye, kaye, keiȝe, from Old English cǣġ, cǣġe, cǣga (key, solution, experiment) (whence also Scots key and kay (key)), of uncertain origin.[1] Related to Old English cǣggian (to lock, shut). The only sure cognates are Saterland Frisian Koai (key), West Frisian kaai (key), and North Frisian kay (key). Possibly from Proto-Germanic *kēgaz, *kēguz (stake, post, pole), from Proto-Indo-European *ǵogʰ-, *ǵegʰ-, *ǵegʰn- (branch, stake, bush), which would make it cognate with Middle Low German kāk (whipping post, pillory), and perhaps to Middle Dutch keige (javelin, spear) and Middle Low German keie, keige (spear). For the semantic development, note that medieval keys were simply long poles (ending in a hook) with which a crossbar obstructing a door from the inside could be removed from the outside, by lifting it through a hole in the door. Liberman has noted, however, "The original meaning of *kaig-jo- was presumably '*pin with a twisted end.' Words with the root *kai- followed by a consonant meaning 'crooked, bent; twisted' are common only in the North Germanic languages."[2]


key (plural keys)

  1. An object designed to open and close a lock.
    • 1913, Joseph C. Lincoln, chapter 13, in Mr. Pratt's Patients:
      We tiptoed into the house, up the stairs and along the hall into the room where the Professor had been spending so much of his time. 'Twas locked, of course, but the Deacon man got a big bunch of keys out of his pocket and commenced to putter with the lock.
  2. An object designed to fit between two other objects (such as a shaft and a wheel) in a mechanism and maintain their relative orientation.
    • Orientation definition
      The determination of the relative position of something or someone. (1 of 12 orientation definitions)
  3. A crucial step or requirement.
    The key to solving this problem is persistence.
    the key to winning a game
  4. A guide explaining the symbols or terminology of a map or chart; a legend.
    The key says that A stands for the accounting department.
  5. A guide to the correct answers of a worksheet or test.
    Some students cheated by using the answer key.
  6. (computing) One of several small, usually square buttons on a typewriter or computer keyboard, mostly corresponding to text characters.
    Press the Escape key.
  7. (music)
    1. In musical instruments, one of the valve levers used to select notes, such as a lever opening a hole on a woodwind.
    2. In instruments with a keyboard such as an organ or piano, one of the levers, or especially the exposed front end of it, which are depressed to cause a particular sound or note to be produced.
    • Hole definition
      A hollow place or cavity; an excavation; a pit; an opening in or through a solid body, a fabric, etc.; a perforation; a rent; a fissure. (1 of 21 hole definitions)
  8. (music)
    1. The lowest note of a scale; keynote.
    2. In musical theory, the total melodic and harmonic relations, which exist between the tones of an ideal scale, major or minor; tonality.
    3. In musical theory and notation, the tonality centering in a given tone, or the several tones taken collectively, of a given scale, major or minor.
    4. In musical notation, a sign at the head of a staff indicating the musical key.
    the key of B-flat major
    • 1881, R.L. Stevenson, Virginibus Puerisque:
      A girl, it is true, has always lived in a glass house among reproving relatives, whose word was law; she has been bred up to sacrifice her judgments and take the key submissively from dear papa; and it is wonderful how swiftly she can change her tune into the husband's.
    • Staff definition
      A long, straight, thick wooden rod or stick, especially one used to assist in walking. (1 of 11 staff definitions)
  9. (figuratively) The general pitch or tone of a sentence or utterance.
  10. (advertising) A modification of an advertisement so as to target a particular group or demographic.
    • 1998, Mail Order Success Secrets
      Another popular way to key ads and mailings is to use a suite number, room number, department number, desk number, etc. as part of the ordering address. With a classified ad, using such a key may increase your ad cost.
    • Demographic definition
      Of or pertaining to demography.
  11. (botany) An indehiscent, one-seeded fruit furnished with a wing, such as the fruit of the ash and maple; a samara.
    • Botany definition
      The scientific study of plants, a branch of biology. Typically those disciplines that involve the whole plant. (1 of 4 botany definitions)
    • Fruit definition
      In general, a product of plant growth useful to man or animals. (1 of 9 fruit definitions)
  12. (historical) A manual electrical switching device primarily used for the transmission of Morse code.
  13. (cryptography) A piece of information (e.g. a passphrase) used to encode or decode a message or messages.
  14. (Internet) A password restricting access to an IRC channel.
    • 2000, "Robert Erdec", Re: Help; mIRC32; unable to resolve server arnes.si (on newsgroup alt.irc.mirc)
      if you know someone who is in the channel, you can query them and ask for the key.
    • Internet definition
      The specific internet consisting of a global network of computers that communicate using Internet Protocol (IP) and that use Border Gateway Protocol (BGP) to identify the best paths to route those communications.
  15. (databases) In a relational database, a field used as an index into another table (not necessarily unique).
  16. (computing) A value that uniquely identifies an entry in a container.
  17. (basketball) The free-throw lane together with the circle surrounding the free-throw line, the free-throw lane having formerly been narrower, giving the area the shape of a skeleton key hole.
    He shoots from the top of the key.
    • Skeleton Key definition
      A very simple design of key that usually has a cylindrical shaft (sometimes called a "shank") and a single, minimal flat, rectangular tooth or "bit". (1 of 3 skeleton key definitions)
  18. (biology) A series of logically organized groups of discriminating information which aims to allow the user to correctly identify a taxon.
  19. (architecture) A piece of wood used as a wedge.
  20. (architecture) The last board of a floor when laid down.
  21. (masonry) A keystone.
  22. That part of the plastering which is forced through between the laths and holds the rest in place.
  23. (rail transport) A wooden support for a rail on the bullhead rail system.
    • Bullhead Rail definition
      A rail, most commonly used in the United Kingdom, with a head and foot nearly equal in cross-section, that is supported in cast iron chairs and secured by wedges or keys.
  24. The degree of roughness, or retention ability of a surface to have applied a liquid such as paint, or glue.
    The door panel should be sanded down carefully to provide a good key for the new paint.
  25. (cartomancy) The thirty-third card of the Lenormand deck.
  26. (print and film) The black ink layer, especially in relation to the three color layers of cyan, magenta, and yellow. See also CMYK.
  27. (computer graphics, television) A color to be masked or made transparent.
    • 2004, Mark Schmidt, ‎Simon Robinson, Microsoft Visual C# .NET 2003 Developer's Cookbook (page 195)
      You can easily create this type of user interface by creating a bitmap with certain portions set to a predefined color you want to use as the transparency key.
    • 2016, Jerry C. Whitaker, The SBE Broadcast Engineering Handbook:
      There are key controls that adjust the “slice level” or the level at which the key kicks-in and starts cutting a hole for the “fill” [] Chroma key is another form of keying, which derives the key cutter or hole from a selected color.
    • Television definition
      An electronic communication medium that allows the transmission of real-time visual images, and often sound. (1 of 4 television definitions)
    • Color definition
      The spectral composition of visible light. (1 of 23 color definitions)
Derived terms
Related terms
The translations below need to be checked and inserted above into the appropriate translation tables, removing any numbers. Numbers do not necessarily match those in definitions. See instructions at Dictionary:Entry layout § Translations.

See also


key (comparative more key, superlative most key)

  1. Indispensable, supremely important.
    He is the key player on his soccer team.
    • 2007, Mark H. Moss, Shopping as an Entertainment Experience (page 46)
      Lukas intimates that one of Disney's key attractions was "Main Street USA,” which "mimicked a downtown business district just as Southdale" had done.
    • 2014 October 14, David Malcolm, “The Great War Re-Remembered: Allohistory and Allohistorical Fiction”, in Martin Löschnigg; Marzena Sokolowska-Paryz, editors, The Great War in Post-Memory Literature and Film[1], Walter de Gruyter GmbH & Co KG., →ISBN, page 173:
      The question of the plausibility of the counter-factual is seen as key in all three discussions of allohistorical fiction (as it is in Demandt's and Ferguson's examinations of allohistory) (cf. Rodiek 25–26; Ritter 15–16; Helbig 32).
  2. Important, salient.
    She makes several key points.
    • 2006, Edwin Black, chapter 2, in Internal Combustion[2]:
      Throughout the 1500s, the populace roiled over a constellation of grievances of which the forest emerged as a key focal point. The popular late Middle Ages fictional character Robin Hood, dressed in green to symbolize the forest, dodged fines for forest offenses and stole from the rich to give to the poor. But his appeal was painfully real and embodied the struggle over wood.
    • 2011 September 29, Jon Smith, “Tottenham 3 - 1 Shamrock Rovers”, in BBC Sport[3]:
      With the north London derby to come at the weekend, Spurs boss Harry Redknapp opted to rest many of his key players, although he brought back Aaron Lennon after a month out through injury.


key (third-person singular simple present keys, present participle keying, simple past and past participle keyed)

  1. To fit (a lock) with a key.
  2. To fit (pieces of a mechanical assembly) with a key to maintain the orientation between them.
  3. To mark or indicate with a symbol indicating membership in a class.
    • 1996 January, Garden Dsign Ideas, second printing, Taunton Press, →ISBN, page 25,
      So I worked on a tissue-paper copy of the perimeter plan, outlining groupings of plants of the same species and keying them with letters for the species.
    • 2001, Bruce M. Metzger, The Bible in Translation, →ISBN, page 87,
      The volume closes with thirty pages of "Notes, critical and explanatory," in which Thomson provides seventy-six longer or shorter notes keyed to specific sections of the synopsis.
    • 2002, Karen Bromley, Stretching Students' Vocabulary, →ISBN, page 12,
      Talk about similarities between the words and write them below to the left of the anchor, keying them with a plus sign (+). Talk about the characteristics that set the words apart and list them below the box to the right, keying them with a tilde sign (~).
    • 2007, Stephen Blake Mettee, Michelle Doland, and Doris Hall, compilers, The American Directory of Writer's Guidelines, 6th ("2007–2008") edition, →ISBN, page 757,
      Indicate the comparative value of each heading by keying it with a number in pencil, in the left margin, as follows: []
    • Mark definition
      Boundary, land within a boundary.
      1. A boundary; a border or frontier.
      2. A boundary-post or fence.
      3. A stone or post used to indicate position and guide travellers.
      4. A type of small region or principality.
      5. A common, or area of common land, especially among early Germanic peoples.
      (1 of 35 mark definitions)
  4. (telegraphy and radio telegraphy) To depress (a telegraph key).
    • Radio Telegraphy definition
      The transmission of Morse code (etc) using radio
  5. (radio) To operate (the transmitter switch of a two-way radio).
  6. (computing) (more usually to key in) To enter (information) by typing on a keyboard or keypad.
    Our instructor told us to key in our user IDs.
  7. (colloquial) To vandalize (a car, etc.) by scratching with an implement such as a key.
    He keyed the car that had taken his parking spot.
  8. To link (as one might do with a key or legend).
    • 1960, Richard L. Masland, "Classification of the Epilepsies", in Epilepsia, volume 1, page 516,
      The American Heart Association has prepared their own guide to classification and, keying it with the Standard Nomenclature of Diseases, have done much to encourage a concise yet complete diagnosis.
    • 1976, Nicholas Askounes Ashford, Crisis in the Workplace: Occupational Disease and Injury[4], page 19:
      The workman's compensation system rests on incentives (premium payments) that are keyed to the immediate and relatively undeniable nature of injuries; []
    • 2006, Deborah Blum, Mary Knudson and Robin Marantz Henig, A Field Guide for Science Writers: The Official Guide of the National Association of Science Writers[5], page 63:
      It also features special issues on "Live Longer, Better, Wiser," men's health, women's health, and issues keyed to important "disease weeks."
  9. (intransitive, biology, chiefly taxonomy) To be identified as a certain taxon when using a key.
    • Identified definition
      simple past tense and past participle of identify
  10. (advertising, transitive) To modify (an advertisement) so as to target a particular group or demographic.
    • 1936, John Freeman Pyle, Marketing Principles, Organization and Policies (page 711)
      Keying advertisements and counting the number of inquiries received or the number of coupons returned to indicate the "pulling power" of a particular piece of copy or the coverage of a particular advertising medium.
    • 1998, Mail Order Success Secrets
      Another popular way to key ads and mailings is to use a suite number, room number, department number, desk number, etc. as part of the ordering address. With a classified ad, using such a key may increase your ad cost. Why? Because you're using an extra word or two to key the ad.
  11. To attune to; to set at; to pitch.
    • 1930, Norman Lindsay, Redheap, Sydney: Ure Smith, published 1965, page 23:
      To Ethel alone she addressed a stray remark, keyed below the sound of other voices.
  12. To fasten or secure firmly; to fasten or tighten with keys or wedges.
    (Can we find and add a quotation of Francis to this entry?)
Derived terms


Etymology 2

Variant of cay, from Spanish cayo, from Taíno cayo (small island)

Alternative forms


key (plural keys)

  1. One of a string of small islands.
    the Florida Keys
Derived terms

Etymology 3


key (plural keys)

  1. Alternative form of quay.
    • Quay definition
      A stone or concrete structure on navigable water used for loading and unloading vessels; a wharf.

Etymology 4

Abbreviating kilogram, via kilo.


key (plural keys)

  1. (slang) Clipping of kilogram (especially of a recreational drug)
    Synonym: kay
    • 2010, David J. Silas, Da Block (page 41)
      So starting with ten keys of cocaine and two keys of heroin, Derrick put his plan in motion. Soon every major drug dealer and gang chief from Chicago Avenue to Evanston was in his pocket.
    • Kilogram definition
      In the International System of Units, the base unit of mass; conceived of as the mass of one litre of water, but now defined by taking the fixed numerical value of the Planck constant h to be 6.626 070 15 × 10 when expressed in units of kg⋅m⋅s. Symbol: kg (1 of 2 kilogram definitions)
    • Kay definition
      Abbreviation of okay.


Central Kurdish key definition


key (key)

  1. when
    • When definition
      At what time? At which time? Upon which occasion or circumstance? Used to introduce direct or indirect questions about time. (1 of 3 when definitions)

Manx key definition

Etymology 1

(This etymology is missing or incomplete. Please add to it, or discuss it at the Etymology scriptorium.)


key m (genitive singular , plural )

  1. cream
Derived terms

Etymology 2

(This etymology is missing or incomplete. Please add to it, or discuss it at the Etymology scriptorium.)


key m (genitive singular keyee)

  1. (nautical) quay


Manx mutation
Radical Lenition Eclipsis
key chey gey
Note: Some of these forms may be hypothetical. Not every
possible mutated form of every word actually occurs.