- The definition of a key is a metal instrument used for opening and closing a lock or operating a mechanical device.
An example of key is what people use to open their car doors and start the engine.
A woman receives the key to the car.
key definition by Webster's New World
- an instrument, usually of metal, for moving the bolt of a lock and thus locking or unlocking something
- any of several instruments or mechanical devices resembling or suggesting this in form or use; specif.,
- a device to turn a bolt, etc.: a skate key, a watch key
- a pin, bolt, wedge, cotter, or similar device put into a hole or space to lock or hold parts together
- something that completes or holds together the parts of another thing, as the keystone of an arch or a roughened surface forming a secure base for plaster
- any of a set of levers, or the disks, buttons, etc. connected to them, pressed down in operating a piano, accordion, clarinet, typewriter, linotype, word processor, etc.
- a device for opening or closing an electric circuit
- a small metal piece for fastening a wheel, pulley, etc. to a shaft
- a key-shaped emblem presented as an honor: the key to the city
- something regarded as like a key in opening or closing a way, revealing or concealing, etc.; specif.,
- a place so located as to give access to or control of a region: Vicksburg was the key to the lower Mississippi
- a thing that explains or solves something else, as a book of answers, the explanations on a map, the code to a system of pronunciation, etc.
- a controlling or essential person or thing
- tone of voice; pitch
- tone or style of thought or expression: in a cheerful key
- relative intensity of feeling: low-key remarks on a volatile subject
- the tone of a picture with regard to lightness or darkness or intensity of color
Origin: < keyhole, its former shapeBasketball either of the marked or painted areas on the court near each basket, extending from the end line to the top of the circle that surrounds the foul line
- Biol. an arrangement or listing of the significant characteristics of a group of organisms, used as a guide for taxonomic identification
- Bot. key fruit
- Comput. a field in a record, used to uniquely identify that record
- Obsolete the keynote of a scale
- a system of related notes or tones based on and named after a certain note (keynote, tonic) and forming a given scale; tonality
- the main tonality of a composition
Origin: Middle English keye ; from Old English cæge, akin to Old Frisian kei, kēia, to secure, guard
Origin: ; from pronunciation of 1st syllable of Spanish kilogramo, kilogram
key definition by American Heritage Dictionary
noun pl. keys keys
- a. A notched and grooved, usually metal implement that is turned to open or close a lock.b. A similar device used for opening or winding: the key of a clock; a can that has a key attached.
- A means of access, control, or possession.
- a. A vital, crucial element.b. A set of answers to a test.c. A table, gloss, or cipher for decoding or interpreting.
- A device, such as a wedge or pin, inserted to lock together mechanical or structural parts.
- Architecture The keystone in the crown of an arch.
- a. A button or lever that is depressed to operate a machine.b. A button that is depressed to cause a corresponding character or function to be typed or executed by a typewriter or to be accepted as input by a computer.c. Music A button or lever that is depressed with the finger to produce or modulate the sound of an instrument, such as a clarinet or piano.
- Music a. A tonal system consisting of seven tones in fixed relationship to a tonic, having a characteristic key signature and being the structural foundation of the bulk of Western music; tonality.b. The principal tonality of a work: an etude in the key of E.
- The pitch of a voice or other sound.
- A characteristic tone or level of intensity, as of a speech or sales campaign. Often used in combination: high-key; low-key.
- Botany A samara.
- An outline of the distinguishing characteristics of a group of organisms, used as a guide in taxonomic identification.
- Basketball An area at each end of the court between the base line and the foul line and including the jump-ball circle at the foul line: a jump shot from the top of the key.
- To lock with or as if with a key.
- Architecture To furnish (an arch) with a keystone.
- Music To regulate the pitch of.
- To bring into harmony; adjust or adapt.
- To supply an explanatory key for.
- a. To operate (a device), as for typesetting, by means of a keyboard.b. To enter (data) into a computer by means of a keyboard.
- To identify (a biological specimen).
- To vandalize or mar by scratching with a key: Vandals keyed the cars left in the parking garage.
- To pay close attention; focus: improved service by keying on customer complaints; keyed in on the main points of the lecture.
- Sports To watch or cover an opposing player closely in an effort to limit the player's effectiveness. Used with on: “[She] still carries the burden of scoring … even though opponents key on her throughout every game” (Josh Barr).
Origin: Middle English kai, kei, from Old English cǣg.
noun pl. keys keys
Origin: Alteration (influenced by key, variant of quay) of Spanish cayo; see cay.
noun pl. keys keys Slang
Origin: Shortening and alteration of kilogram.
, Francis Scott 1779-1843.
key - Computer Definition
- A small mechanical device for opening, closing, or switching electrical circuits. A telegraph key, for example, is used to open and close an electrical circuit to send short and long pulses of electric current. See also keyboard, keypad, and KTS.
- A string of bits used for encrypting and decrypting information. A private key is known to only one person, typically the sender. A public key is known to more than one person, typically both the sender and the receiver, and is published and freely available from a public key infrastructure (PKI) or certificate authority (CA). See also CA, encryption, PKI, private key encryption, and public key encryption.
The value needed to encrypt or decrypt a message. Keys can be symmetric or asymmetric. If someone wanted to keep information secret from another, he or she could utilize one of two strategies: either hide the fact that the information exists, or make the information that exists unintelligible to another.
Cryptography is the act of securing information by encrypting it, and cryptanalysis is the act of decrypting encrypted data to make a message intelligible. Cryptology is the area of mathematics that includes both cryptography and cryptanalysis.
Modern cryptography uses algorithms, or complex mathematical equations, and secret keys to decrypt and encrypt information. A key is a number or a string that is typically fewer than 20 characters. Symmetric keys use the same key for decryption and encryption, whereas asymmetric keys are produced in pairs—one key encrypts the information and the other, “mirrored” key decrypts it. Thus, someone having only one key could not figure out the other key.
A common question in security pertains to differences between 40-bit and 128-bit encryption in Internet browsers. The easiest way to break encryption in order to read the plaintext is simply to try all possible keys. To help indicate the relative degree of difficulty in carrying out this task, it is important to realize that a 40-bit key has one trillion combinations. So, it would take a lone computer many weeks to attempt all these combinations. A cracker with considerable time on his or her hands would likely need just a few weeks to decrypt a message sent across the Internet with a 40-bit browser.
Furthermore, every increase in key length means that the key will take double the time to crack. For argument’s sake, if a computer needs one week to crack a 40-bit key, it will take twice as long to break a 41-bit key—and for a 128-bit key, it will need an estimated 309,485,009,821,345,068,724,781,056 times longer to break it.
Graham, R. Hacking Lexicon. [Online, 2001.] Robert Graham Website: http://www.linuxsecurity.com/resource_files/documentation/hacking-dict.html; Simpson, S. Cryptography Defined/Brief History. [Online, Spring, 1997.] University of Texas Economics Website: http://www.eco.utexas.edu/faculty/Norman/BUS.FOR/course.mat/SSim/history .html.
key - Cultural Definition
The main or central note of a piece of music (or part of a piece of music). Each key has its own scale, beginning and ending on the note that defines the octave of the next scale. The key of C-major uses a scale that starts on C and uses only the white keys of the piano. In a piece composed in the key of C, the music is likely to end on the note C, and certain combinations of notes based on C will predominate.
key - Phrases/Idioms
key (in) on
out of key
key - Science Definition
Variant of keyhole