From Middle English keye, kaye, keiȝe, from Old English cǣġ (“key, solution, experiment”) (whence also Scots key and kay (“key”)), from Anglo-Frisian Proto-West Germanic *kaiju, of uncertain origin. The only sure cognates are Saterland Frisian Koai (“key”), West Frisian kaai (“key”), and North Frisian kai, koie (“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."
An object designed to open and close a lock or to activate or deactivate something, especially a length of metal inserted into a narrow opening on the lock to which it is matched (keyed).
This key is to the backdoor.
insert the key into the lock (formal); put the key in the lock (informal)
2 more examples
apartment key; room key; spare key
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.1913, Joseph C[rosby] Lincoln, chapter XIII, in Mr. Pratt’s Patients, New York, N.Y.; London: D[aniel] Appleton and Company, →OCLC:
2
A card or fob that electronically signals a lock to open.
Internet A password restricting access to an IRC channel.
if you know someone who is in the channel, you can query them and ask for the key.2000, Robert Erdec, “Re: Help; mIRC32; unable to resolve server arnes.si”, in alt.irc.mirc (Usenet):
5
Any of various tools comparable to a wrench (spanner) or driver, which have a specialized end that matches a fixture, analogously to a lock's key.
The exterminator will bring a key thingy that can open the bait boxes.
That part of the plastering which is forced through between the laths and that holds the rest in place.
11
Rail transport, Railways, Transport A wooden wedge, driven sideways between a bullhead rail and a cast-iron chair, to keep the rail securely in position.
The key to winning that game is your strategy at the beginning.
4 more examples
Those who are accustomed to reason have got the true key of books.a. 1705, John Locke, “Of the Conduct of the Understanding”, in Posthumous Works of Mr. John Locke: […], London: […] A[wnsham] and J[ohn] Churchill, […], published 1706, →OCLC:
who keeps the keys of all the creeds1850, [Alfred, Lord Tennyson], “(please specify |part=Prologue or Epilogue, or |canto=I to CXXIX)”, in In Memoriam, London: Edward Moxon, […], →OCLC:
The PEOPLE'S DAILY today front pages a news item in column one in the experience of Yuhsi County in Yunnan which "mastered the law of agricultural field management, and found the key to increasing autumn grain production."1960 August 29 [1960 August 26], “Higher Autum Grain Yield is Possible”, in Daily Report: Foreign Radio Broadcasts, number 168, Foreign Broadcast Information Service, sourced from Peking NCNA, translation of original in Chinese, →OCLC, Communist China: National Affairs, page BBB 2-BBB 3:
Imagination is the key to creation. Whatever you can imagine becomes reality or is reality. That's the way it works.2015, Omnec Onec, Simply Wisdom and Love:
13
Broadly, Figuratively An idea, theory or observation that explains, justifies or renders (something) comprehensible.
The key to his proposal is that he thinks this company is dying and needs radical change.
A small guide explaining symbols, abbreviations or terminology, especially the legend on a map or chart.
map key
The key says that A stands for the accounting department.
16
A guide to the correct answers of a worksheet or test.
Some students cheated by using the key.
17
Biology, Natural sciences A series of logically organized groups of discriminating information which aims to allow the user to correctly identify a taxon; a taxonomic key.
18
Computing, Engineering, Mathematics, Natural sciences, Physical sciences, Sciences A value that uniquely identifies an entry in a container.
19
Computing, Databases, Engineering, Mathematics, Natural sciences, Physical sciences, Sciences In a relational database, a field used as an index into another table (not necessarily unique).
› Senses relating to a set of features that…
20
Computing, Engineering, Mathematics, Natural sciences, Physical sciences, Sciences One of several small, usually square buttons on a typewriter or computer keyboard, mostly corresponding to text characters.
Press the Escape key.
A key; B key, etc.
21
Entertainment, Lifestyle, Music In musical instruments, one of the valve levers used to select notes, such as a lever opening a hole on a woodwind.
piano key
22
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.
23
Entertainment, Lifestyle, Music A scale or group of pitches constituting the basis of a musical composition.
the key of B-flat major
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.1881, R.L. Stevenson, Virginibus Puerisque:
Entertainment, Lifestyle, Music In musical theory, the total melodic and harmonic relations, which exist between the tones of an ideal scale, major or minor; tonality.
26
Entertainment, Lifestyle, Music 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.
27
Entertainment, Lifestyle, Music In musical notation, a sign at the head of a staff indicating the musical key.
2. Queen.[…]Deere Glasse of Ladies Bid him that we whom flaming war doth scortch, Vnder the shaddow of his Sword, may coole us: Require him he advance it ore our heades; Speak't in a womans key: like such a woman As any of us three; weepe ere you faile; lend us a knee; But touch the ground for us no longer time Then a Doves motion, when the head's pluckt off: Tell him if he i'th blood cizd field, lay swolne Showing the Sun his Teeth; grinning at the Moone What you would doe.1613–1614 (date written), John Fletcher, William Shak[e]speare, The Two Noble Kinsmen: […], London: […] Tho[mas] Cotes, for Iohn Waterson; […], published 1634, →OCLC, Act I, scene i, page 1:
?, William Cowper, Conversation You fall at once into a lower key.
1 more example
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.1998, Mail Order Success Secrets:
› A scale or group of pitches constituting the… › The general pitch or tone of a sentence or utterance.
Biology, Botany, Natural sciences An indehiscent, one-seeded fruit furnished with a wing, such as the fruit of the ash and maple; a samara.
32
Ball games, Basketball, Games, Hobbies, Lifestyle, Sports 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.
33
Cartomancy, Human sciences, Mysticism, Philosophy, Sciences The thirty-third card of the Lenormand deck, which features an image of a key.
› Senses related to colors.
34
Art, Arts The overall color tone of a painting or other visual art, with a high key indicating generally light colors and a low key indicating generally dark colors.
35
The black ink layer, especially in relation to the three color layers of cyan, magenta, and yellow. See also CMYK.
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.2004, Mark Schmidt, Simon Robinson, Microsoft Visual C# .NET 2003 Developer's Cookbook, page 195:
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.2016, Jerry C. Whitaker, The SBE Broadcast Engineering Handbook:
37
Historical A manual electrical switching device primarily used for the transmission of Morse code.
38
The degree of roughness, or the ability of a surface to retain an applied liquid, such as paint or glue.
The door panel should be sanded down carefully to provide a good key for the new paint.
From Middle English keye, kaye, keiȝe, from Old English cǣġ (“key, solution, experiment”) (whence also Scots key and kay (“key”)), from Anglo-Frisian Proto-West Germanic *kaiju, of uncertain origin. The only sure cognates are Saterland Frisian Koai (“key”), West Frisian kaai (“key”), and North Frisian kai, koie (“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."
1
Usually Indispensable, supremely important.
He is the key player on his soccer team.
Paradoxically enough, however, in general only the parties of the Left have done most to spread the belief that it was the numerical strength of the opposing material interests which decided political issues, whereas in practice these same parties have regularly and successfully acted as if they understood the key position of the intellectuals.1949, F. A. Hayek, “The Intellectuals and Socialism”, in University of Chicago Law Review, volume 16, number 3, Chicago: University of Chicago, →DOI, page 418:
3 more examples
Lukas intimates that one of Disney's key attractions was "Main Street USA,” which "mimicked a downtown business district just as Southdale" had done.2007, Mark H. Moss, Shopping as an Entertainment Experience, page 46:
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).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, Walter de Gruyter GmbH & Co KG., →ISBN, page 173:
The enemy is moving troops through a key area. Distrupt their activities to open some holes in their defenses.2017, BioWare, Mass Effect: Andromeda (Science Fiction), Redwood City: Electronic Arts, →OCLC, PC, scene: Disrupt Enemy Movements:
2
Usually Important, salient.
She makes several key points.
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.2006, Edwin Black, chapter 2, in Internal Combustion:
1 more example
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.2011 September 29, Jon Smith, “Tottenham 3 - 1 Shamrock Rovers”, in BBC Sport:
key
verb
Etymology
From Middle English keye, kaye, keiȝe, from Old English cǣġ (“key, solution, experiment”) (whence also Scots key and kay (“key”)), from Anglo-Frisian Proto-West Germanic *kaiju, of uncertain origin. The only sure cognates are Saterland Frisian Koai (“key”), West Frisian kaai (“key”), and North Frisian kai, koie (“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."
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.
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.1996 January, Garden Dsign Ideas, second printing, Taunton Press, →ISBN, page 25:
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.2001, Bruce M. Metzger, The Bible in Translation, →ISBN, page 87:
2 more examples
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 (~).2002, Karen Bromley, Stretching Students' Vocabulary, →ISBN, page 12:
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: […]
Computing, Engineering, Mathematics, Natural sciences, Physical sciences, Sciences (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).
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.1960, Richard L. Masland, “Classification of the Epilepsies”, in Epilepsia, volume 1, page 516:
The workman's compensation system rests on incentives (premium payments) that are keyed to the immediate and relatively undeniable nature of injuries; […]1976, Nicholas Askounes Ashford, Crisis in the Workplace: Occupational Disease and Injury, page 19:
1 more example
It also features special issues on "Live Longer, Better, Wiser," men's health, women's health, and issues keyed to important "disease weeks."2006, Deborah Blum, Mary Knudson, Robin Marantz Henig, A Field Guide for Science Writers: The Official Guide of the National Association of Science Writers, page 63:
9
Biology, Natural sciences, Taxonomy To be identified as a certain taxon when using a key.
10
Advertising, Business, Marketing To modify (an advertisement) so as to target a particular group or demographic.
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.1936, John Freeman Pyle, Marketing Principles, Organization and Policies, page 711:
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.1998, Mail Order Success Secrets:
11
To attune to; to set at; to pitch.
To Ethel alone she addressed a stray remark, keyed below the sound of other voices.1930, Norman Lindsay, Redheap, Sydney, N.S.W.: Ure Smith, →OCLC, page 23:
12
To fasten or secure firmly; to fasten or tighten with keys or wedges.
they Mouldered and keyed the Portico Arches with Pieces of Stone, because Brick was not strong enough1744, Roger North, The Life of the Honourable Sir Dudley North:
13
To prepare for plastering by adding the key (that part of the plastering which is forced through between the laths and holds the rest in place).
14
To provide an arch with a keystone.
The last arch in the permanant ^([sic]) bridge was keyed on March 26, 1850, and a single track was brought into use for goods trains on July 20.1950 September, “Centenary of the Royal Border Bridge”, in Railway Magazine, page 637:
After keying the background, you’d be left with a transparent background, where you can install anything—from images to videos that blend seamlessly into the main subject of the shot.2021 September 11, Anina Ot, “What Is a Green Screen and How Does It Work?”, in MakeUseOf:
Slang A kilogram, especially of a recreational drug.
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.2010, David J. Silas, Da Block, page 41:
key
noun
Etymology Clipping of key position.
1
A key position player (a tall forward or defender).
Australian rules football
"It just means that one of them here and there will need to play on a small-to-medium forward (instead of Riewoldt) which is fine. Our keys are pretty agile."2023 April 7, “'Bit of a surprise': Dogs bemused by Tigers' selection call”, in Australian Football League, retrieved 27 Jul 2025: