key
Pluralkeys
Pluralkeys
- 1A small metal object, or a card, used to open or close a lock.
Like a special shape that fits one lock and no other.
She turned the key and the door clicked open.
He lost his house keys somewhere in the park.
UsageSay the key to the door. You turn a key.
Note
- 2Very important, or the most important.
She made a key point during the meeting.
Sleep is a key factor in good health.
UsageUse it before a noun, a key point, or after is: Timing is key.
Similarimportant, major, significant, main, principal
Oppositeminor, unimportant, trivial, insignificant
Note
- 3The one thing you most need to make something happen, or to understand or solve something.
Like the last step that makes the whole plan work.
Hard work is the key to passing the exam.
Patience was the key to fixing the broken clock.
UsageSay the key to something: the key to winning.
Similarsecret, answer, solution
Note
- 4One of the small buttons you press to type letters or numbers.
Like a button on a remote: each one does its own thing.
The space key is the longest one on the bottom row.
She pressed the wrong key and deleted her work.
Similarbutton
Note
- 5
- 6The group of musical notes that a song is built on.
Like the home note a tune keeps coming back to.
The song is written in the key of C.
They changed the key to make it easier to sing.
UsageSay a song is in the key of C.
Note
- 7One of the parts you press on a piano or other instrument to play a note.
Like a button that plays a sound each time you push it.
She pressed a key and a soft note filled the room.
The piano had one key that stuck whenever he played.
Note
- 8
Less common meanings
- 9A code of letters and numbers that lets you start using a program, game, or online service.
Type the key from the box to start using the program.
My brother bought me a key for the new game online.
Similarcode
Note
- 10A list of the correct answers to a test or worksheet.
Like a list that shows which answers are right.
The teacher used the key to grade our tests quickly.
He peeked at the answer key before finishing.
UsagePeople often say answer key.
- 11A small guide that explains the symbols on a map or chart.
Like a small list that tells you what each picture stands for.
Look at the key to learn what each color means.
The map's key showed which lines were rivers.
Similarlegend
- 12In computing, a value used to find or label a piece of stored data.
Like a name tag that points to one exact box.
Each item has its own key so the program can find it.
The program looks up the value by its key.
Similaridentifier
Note
- 13
- 14
- 15
- 16A set of steps or questions that helps you find out what kind of plant or animal something is.
Like a game of twenty questions where each answer brings you closer to the right name.
We used a key to find out what kind of beetle we had caught.
The bird book has a key at the back for telling ducks apart.
Note
- 17A small tool used to turn, tighten, or wind something, similar to a wrench or screwdriver.
Like a small tool that grips a part and turns it.
She grabbed an Allen key to put the bookshelf together.
He wound the old clock with a small brass key.
UsageMost often in names like Allen key or clock key.
Similarwrench, spanner, driver
Note
- 18In basketball, the painted area near the basket where players stand for free throws.
Like a marked-off zone on the floor where much of the action happens.
The center backed into the key, looking for an easy basket.
No defender can stay in the key for more than three seconds.
UsageSay in the key and the top of the key.
Note
- 19A kilogram, usually of an illegal drug.
The dealer was caught with a key of cocaine in the trunk.
They sold half a key to an undercover officer.
UsageUse kilo for normal weights.
Similarkilo
Note
- 20A small part that fits between two pieces of a machine to hold them in the same position.
Like a small wedge that stops two parts from twisting apart.
The machinist filed a key to lock the gear onto the shaft.
A worn key let the pulley slip on its axle.
- 21To join parts of a machine with a key so they stay lined up.
Like fitting a tab into a slot so two parts can't twist apart.
Technicians key each gear to its shaft during assembly.
They keyed the flywheel so it always sat at the same angle.
- 22To set up a lock so a particular key works in it.
Like matching one special key to one special lock so only it opens.
The locksmith keyed both locks so one key opens the front and back doors.
Ask the locksmith to key the new lock to match the old one.
UsageLocks keyed alike open with one key.
- 23
- 24
- 25The wedge-shaped stone at the top of an arch that holds the other stones in place.
Like the middle piece that keeps a stone arch from falling.
Masons set the key last to lock the whole arch together.
The stone key at the top of the arch has the date 1742 cut into it.
UsageMost people say keystone.
Note
- 26A hand-operated switch used to tap out messages in Morse code.
Like a button you tap quickly to send dots and dashes.
The operator tapped a distress call on the brass key.
She practiced sending letters with a telegraph key for hours.
Note
- 27A dry, winged fruit with a single seed, like the spinning fruit of a maple tree.
Like a tiny spinning blade that carries a seed through the air.
Children love to toss a maple key and watch it spin down.
An ash tree drops hundreds of keys across the yard each fall.
UsagePeople say maple keys and ash keys.
Similarsamara
Note
- 28The roughness of a surface that helps paint or glue stick to it.
Rub the old tiles with sandpaper to give the glue a good key.
Smooth glass has almost no key, so the paint peeled off within a week.
UsageSay sanding gives paint a good key.
Similartooth
Note
- 29In color printing, the layer of black ink added to the cyan, magenta, and yellow layers.
- 30The note that a music scale starts on, the bottom note.
- 31How the notes of a major or minor scale relate to each other.
- 32The signs at the start of a line of music that show its key.
- 33A change made to an ad so it targets one group of people.
- 34A secret word you must type to get into an IRC chat room.
- 35A wedge made of wood.
- 36The last board put down when making a floor.
- 37Plaster that pushes between thin strips of wood and holds the rest on.
- 38A wooden wedge that holds a railway rail tight in place.
- 39Card number 33 in a Lenormand fortune-telling deck.
- 40A color in a picture or video that is made see-through.
- 41A tall player in a main attacking or defending spot in Australian football.
- 42To push down on the switch of a telegraph.
- 43To press the button that makes a two-way radio send.
- 44Of a plant or animal, to turn out to be a certain kind when checked with a key.
- 45To change an ad so it reaches one group.
- 46To fix something firmly in place with wedges.
- 47To get a wall ready so plaster will stick to it.
- 48To put the top middle stone into an arch.
- 49To replace one color in a video with another picture.
- 50An old spelling of quay, a place where boats stop.
Showing meanings only.
Practice
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Origins
From Old English cǣġ, meaning "key." Its origin is uncertain.
Checked 1 Nov 2026 · 2 facts
- Key derives from Old English cǣġ, meaning "key". en.wiktionary.org
- Its ultimate origin is uncertain. en.wiktionary.org
A different spelling of "cay," which came from Spanish cayo and originally from the Taíno word for a small island.
Checked 1 Nov 2026 · 3 facts
- Key is a variant spelling of cay. en.wiktionary.org
- Cay came from Spanish cayo. en.wiktionary.org
- Spanish cayo came from a Taíno word meaning small island. en.wiktionary.org
A shortened form of "kilogram" or "kilo."
Checked 1 Nov 2026 · 1 fact
- Key is a shortened form of kilogram or kilo. en.wiktionary.org