DictionaryAI

key

SayKEE/ki//kiː/

Pluralkeys

50 meanings of key

Practice

  1. 1
    for a locknouncountable
    An object used to open and close a lock, usually a shaped piece of metal but also an electronic card or fob.

    The locksmith cut a new key for the front door.

    Each key on the ring opened a different office.

    UsageA key to or for a door or lock. You turn a key in a lock.

    Note

    Even in Old English the word could also mean "solution," so its later figurative meanings did not have far to travel. A big bunch of keys, as in Joseph C. Lincoln's Mr. Pratt's Patients (1913), is still the plain picture.

    Checked 2 Nov 2026 · 2 facts

    • Joseph C. Lincoln wrote Mr. Pratt's Patients, first published in 1913; the original title page confirms the date. archive.org
    • The novel contains a literal bunch of keys. archive.org
  2. 2
    vitaladjective
    Important and standing out as significant.

    The witness shared a key detail that changed the case.

    Location is a key consideration when buying a home.

    UsageMost often before a noun: a key detail, key players.

    Similarimportant, major, significant, main, principal

    Oppositeminor, unimportant, trivial, insignificant

    Note

    In this use the sense ranges from indispensable to simply important or salient, and it is common in reports and match coverage, as in several key points. In a BBC Sport report from 2011, Harry Redknapp rests his key players before a derby. So key players can mean the ones a team cannot do without, or simply its leading names.

    Checked 30 Oct 2026 · 1 fact

    • The 2011 BBC report describes Redknapp resting key players before a derby. bbc.com
  3. 3
    the secret tonouncountable
    Something that is crucial for achieving a result, or that explains or solves a problem or mystery.

    Clear communication is the key to a successful project.

    Discipline became the key to her steady improvement.

    UsageFollowed by to and a noun or -ing form: the key to success, the key to winning.

    Similarsecret, answer, solution

    Note

    Here whatever unlocks a problem takes over from the lock-opening object. Today the word is followed by to and then a noun or an -ing form: the key to winning, the key to solving it. Older writers used of instead. Locke speaks of "the true key of books", and Tennyson in 1850 of one "who keeps the keys of all the creeds".

    Checked 30 Oct 2026 · 5 facts

  4. 4
    computer buttonnouncountable
    One of the small, usually square buttons on a typewriter or computer, most of them standing for text characters.

    He hit the return key to start a new line.

    Several keys on the old typewriter were stuck.

    Similarbutton

    Note

    The typewriter and the computer share this sense. From this button comes the verb "to key in", which means entering information by pressing keys rather than writing it out.

    Checked 2 Nov 2026 · 2 facts

    • The button sense applies to both typewriters and computer keyboards. en.wiktionary.org
    • Key in is formed from key in its keyboard-button sense and means entering information using those keys. en.wiktionary.org
  5. 5
    secret codenouncountable
    A piece of information, such as a password, used to encode or decode messages.

    The two agents shared a key for decoding their messages.

    Anyone who steals the key can read every encrypted file.

    Similarcode, password

    Note

    Cryptography borrows the lock-and-key picture. In symmetric encryption, the key is the one piece that must stay secret, because whoever holds it can read everything it protects. The metaphor sits comfortably on an old word: Old English cǣġ already meant "solution" as well as "key." Keep it distinct from the lookup value in programming, which finds an entry rather than unlocking a message.

    Checked 30 Oct 2026 · 3 facts

    • Cryptographic terminology uses the metaphor of physical keys and locks. static.usenix.org
    • This describes symmetric encryption. In public-key encryption, the public encryption key may be shared; decryption requires the corresponding secret private key. csrc.nist.gov
    • English key descends from Old English cǣġ, which meant both key and solution. en.wiktionary.org
  6. 6
    musical scalenouncountable
    A scale or group of pitches that forms the basis of a piece of music.

    The symphony shifts to a minor key in its second movement.

    She transposed the song into a higher key for her voice.

    UsageA piece is in a key and can be moved into another: in the key of C, in a minor key.

    Note

    Keys are named by their keynote and their mode: the key of B-flat major, a minor key. A piece is written in a key and can be transposed into another. Stevenson's Virginibus Puerisque (1881) already bends the sense toward behavior: a girl is taught to "take the key submissively from dear papa", following his pitch. That use leads directly to the tone of an utterance.

    Checked 30 Oct 2026 · 2 facts

    • Robert Louis Stevenson wrote Virginibus Puerisque and Other Papers, first published in book form in 1881. en.wikisource.org
    • Stevenson's essay describes a girl's conformity to her father using the quoted musical metaphor; these are the essayist's words. en.wikisource.org
  7. 7
    instrument buttonnouncountable
    On a musical instrument such as a piano, organ or woodwind, one of the levers or buttons pressed to sound or select a particular note.

    He ran his fingers across the keys in a quick scale.

    One ivory key on the old organ no longer made any sound.

    Note

    On a piano, strictly, the key is the whole lever that runs back into the instrument. In everyday use, though, the word usually means the part the player sees and touches at the front. In the plural it often stands for the keyboard as a whole, as when someone runs their fingers across the keys of a piano or organ.

    Checked 30 Oct 2026 · 1 fact

    • This description needs to be restricted to piano keys. Flute keys are fitted to the instrument's body, with pads that close tone holes. yamaha.com
  8. 8
    small islandnouncountable
    A small, low island, usually of sand or coral, as in the Florida Keys.

    The boat anchored beside a sandy key just off the reef.

    A chain of keys stretched south from the mainland.

    UsageBest known from the Florida Keys; elsewhere the same word is often spelled cay.

    Similarcay, islet

    Note

    A different word that happens to share the spelling. Key here is a variant of cay, from Spanish cayo, which goes back to Taíno cayo, "small island". It has no connection with the lock-opening key.

    Checked 2 Nov 2026 · 2 facts

    • The island word is etymologically distinct from the lock-opening word, which comes through Middle English from Old English. en.wiktionary.org
    • Island key is a variant of cay, from Spanish cayo and ultimately Taíno cayo, meaning small island; it has a separate origin from lock-opening key. en.wiktionary.org

Practice

Can you tell the meanings of key apart? Answer 3 quick questions from this page, or write your own sentence and AI will check it.

Origins

Meanings 1–7, 9–18, 20–28

From Middle English keye, from Old English cǣġ ("key, solution"), of uncertain origin. Its only sure cognates are in Frisian, and it may come from Proto-Germanic *kēgaz ("stake, post, pole"), reflecting how early keys could be long hooked poles used to lift a bar off a door from outside.

Checked 1 Nov 2026 · 5 facts

  • English key descends from Middle English keye, which descends from Old English cǣġ. en.wiktionary.org
  • Old English cǣġ meant key or solution. en.wikipedia.org
  • The ultimate origin is uncertain, and the only secure cognates are Frisian. en.wikisource.org
  • A proposed Germanic source is *kēgaz, meaning stake, post or pole. en.wikipedia.org
  • Early keys could be long hooked poles used from outside to lift a door's internal bar, providing a possible semantic explanation. en.wiktionary.org
Meaning 8

Spanish "cayo" is the source of this word, which is another spelling of "cay". Spanish had taken it from the Taíno word "cayo", meaning a small island.

Checked 1 Nov 2026 · 3 facts

Meaning 19

A clipping of kilogram or kilo.

Checked 1 Nov 2026 · 1 fact