• Key


    • RP enPR: , IPA: /kiː/
    • Rhymes: -iː
    • Homophones: cay one pronunciation, quay

    Origin 1

    From Middle English keye, kaye, keiȝe, from Old English cǣġ, cǣġe, cǣga ("key, solution, experiment"), from Proto-Germanic *kēgaz ("stake, post, pole"), from Proto-Indo-European *ǵogh-, *ǵegh- ("branch, stake, bush"), related to Old English cǣggian ("to lock, shut"). Cognate with Scots key, kay ("key"), West Frisian kaai ("key"), North Frisian kay ("key"), Middle Low German kāk ("whipping post, pillory"), and perhaps to Middle Dutch keige ("javelin, spear"), 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.

    Full definition of key



    (plural keys)
    1. An object designed to open and close a lock.
      • 1913, Joseph C. Lincoln, Mr. Pratt's Patients Chapter 13, 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.
    3. A crucial step or requirement.
      The key to solving this problem is persistence.
      the key to winning a game
      • John Locke (1632-1705)Those who are accustomed to reason have got the true key of books.
      • Alfred Tennyson (1809-1892)who keeps the keys of all the creeds
    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) One of a number of rectangular moving parts on a piano or musical keyboard, each causing a particular sound or note to be produced.
    8. (music) One of various levers on a musical instrument used to select notes, such as a lever opening a hole on a woodwind.
    9. (music) A hierarchical scale of musical notes on which a composition is based.
      the key of B-flat major
      • 1881, R.L. Stevenson, :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.
    10. (figurative) The general pitch or tone of a sentence or utterance.
    11. (botany) An indehiscent, one-seeded fruit furnished with a wing, such as the fruit of the ash and maple; a samara.
    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.
    15. (computing) 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 an associative array.
    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.
    18. (biology) A series of logically organized groups of discriminating information which aims to allow the user to correctly identify a taxon.
    19. (slang) Kilogram (though this is more commonly shortened to 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.
    20. (architecture) A piece of wood used as a wedge.
    21. (architecture) The last board of a floor when laid down.
    22. (masonry) A keystone.
    23. That part of the plastering which is forced through between the laths and holds the rest in place.
    24. (rail transport) A wooden support for a rail on the bullhead rail system.
    25. (heraldic charge) The object used to open or close a lock, often used as a heraldic charge.
      The coat of arms of Regensburg is gules two keys in saltire argent.



    1. Indispensable, supremely important.He is the key player for his soccer team.
    2. Important, salient.She makes several key points.
      • 2006, w, Internal Combustion Chapter 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, 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.

    Usage notes

    The first meaning is distinguished by the definite article, as seen in the quotations.


    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 1561580791, 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 0801022827, 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 0439288398, 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 1884956580, page 757,Indicate the comparative value of each heading by keying it with a number in pencil, in the left margin, as follows:...
    4. (telegraphy and radio telegraphy) To depress (a telegraph key).
    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.
      • The workman's compensation system rests on incentives (premium payments) that are keyed to the immediate and relatively undeniable nature of injuries; ...
      • 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.
    10. To fasten or secure firmly; to fasten or tighten with keys or wedges.

    Origin 2

    Variant of cay, from Spanish cayo.

    Alternative forms



    (plural keys)
    1. One of a string of small islands."the Florida Keys"


    Origin 3



    (plural keys)
    1. Alternative form of quay----
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