• Key (lock)
  Key (lock)
  A key is an instrument that is used to operate a lock. A typical key consists of two parts: the blade, which slides into the keyway of the lock and distinguishes between different keys, and the bow, which is left protruding so that torque can be applied by the user. The blade is usually intended to...
  
  , device used to open a lock or door
• Key (cryptography)
  Key (cryptography)
  In cryptography, a key is a piece of information that determines the functional output of a cryptographic algorithm or cipher. Without a key, the algorithm would produce no useful result. In encryption, a key specifies the particular transformation of plaintext into ciphertext, or vice versa...
  
  , a piece of information that controls the operation of a cryptography algorithm (see Subkey
  Subkey
  Subkey can refer to:* A hard-coded parameter in a key schedule* A key in OpenPGP that is bound by a master key...
  
  )
• Key (engineering), a type of coupling used to transmit rotation between a shaft and an attached item

Computing

• Computer keyboard keys
• KeY
  KeY
  The KeY tool is used in formal verification of Java programs.It accepts both specifications written in JML or OCL to Java source files. These are transformed into theorems of dynamic logic and then compared against program semantics which are likewise defined in terms of dynamic logic. KeY is...
  
  , a software verification tool
• Unique key
  Unique key
  In relational database design, a unique key can uniquely identify each row in a table, and is closely related to the Superkey concept. A unique key comprises a single column or a set of columns. No two distinct rows in a table can have the same value in those columns if NULL values are not used...
  
  , a set of fields that uniquely identify any record in a database or registry
• Superkey
  Superkey
  A superkey is defined in the relational model of database organization as a set of attributes of a relation variable for which it holds that in all relations assigned to that variable, there are no two distinct tuples that have the same values for the attributes in this set...
  
  , a similar concept or idea
• Candidate key
  Candidate key
  In the relational model of databases, a candidate key of a relation is a minimal superkey for that relation; that is, a set of attributes such that# the relation does not have two distinct tuples In the relational model of databases, a candidate key of a relation is a minimal superkey for that...
  
  , a minimal superkey
• Keychain (Mac OS), the Apple-created utility for the Macintosh that stores passwords
• Key, which make up the key-value pairs of a hash table
  Hash table
  In computer science, a hash table or hash map is a data structure that uses a hash function to map identifying values, known as keys , to their associated values . Thus, a hash table implements an associative array...
  
  
• .key, file extension used by Keynote

Fiction

• Key (comics)
  Key (comics)
  The Key is the name of two fictional supervillains in the DC Comics universe.-Golden Age Key:The Golden Age Key's sole appearance is in 1951's All Star Comics #57, which features the last Golden Age appearance of the Justice Society of America. In this story, the Key is the head of a major crime...
  
  , a DC Comics supervillain
• Key (Marvel Comics)
  Key (Marvel Comics)
  Key is a fictional mutant character in the Marvel Comics Universe. His first appearance was in Cable vol. 2 #79.-Fictional character biography:...
  
  , a fictional mutant character
• Key the Metal Idol
  Key the Metal Idol
  is an original video animation anime series that was released in Japan from 1994 to 1997. The series consists of fifteen episodes divided into four parts. First Program consists of episodes 1 through 7. Second Program is 8 through 13. Third Program and Final Program are episodes 14 and 15...
  
  , Japanese anime OVA series

Places

• Key Island
  Key Island
  Key Island, with the adjacent Key Reef, is a granite island, with an area of 6 ha, in south-eastern Australia. It is part of Tasmania’s Long Island Group, lying in eastern Bass Strait west of Cape Barren Island in the Furneaux Group....
  
  , Tasmania, Australia
• Florida Keys
  Florida Keys
  The Florida Keys are a coral archipelago in southeast United States. They begin at the southeastern tip of the Florida peninsula, about south of Miami, and extend in a gentle arc south-southwest and then westward to Key West, the westernmost of the inhabited islands, and on to the uninhabited Dry...
  
  , an archipelago of about 1700 such islands in the southeast United States

Music

• Key (instrument)
  Key (instrument)
  A key is a specific part of a musical instrument. The purpose and function of the part in question depends on the instrument.On instruments equipped with tuning machines, violins and guitars, for example, a key is part of a tuning machine. It is a worm gear with a key shaped end used to turn a cog,...
  
  , musical instruments have keys for tuning and keys for playing; such as on a guitar
• Key (music)
  Key (music)
  In music theory, the term key is used in many different and sometimes contradictory ways. A common use is to speak of music as being "in" a specific key, such as in the key of C major or in the key of F-sharp. Sometimes the terms "major" or "minor" are appended, as in the key of A minor or in the...
  
  , a set of notes in music
• Key (singer)
  Key (singer)
  Key also known as Almighty Key is a South Korean idol singer, rapper and dancer. He is most famous as being one of the members of the contemporary R&B and pop quintet boy band, SHINee, under the label of SM Entertainment....
  
   (born 1991), South Korean entertainer
• Key (album), an album by Son, Ambulance
• Key signature
  Key signature
  In musical notation, a key signature is a series of sharp or flat symbols placed on the staff, designating notes that are to be consistently played one semitone higher or lower than the equivalent natural notes unless otherwise altered with an accidental...
  
  , in musical notation and tablature
• Keys can be short for keyboards
  Keyboard instrument
  A keyboard instrument is a musical instrument which is played using a musical keyboard. The most common of these is the piano. Other widely used keyboard instruments include organs of various types as well as other mechanical, electromechanical and electronic instruments...
  
  , a type of musical instrument part of the percussion family

Other uses

• Cay
  Cay
  A cay , also spelled caye or key, is a small, low-elevation, sandy island formed on the surface of coral reefs. Cays occur in tropical environments throughout the Pacific, Atlantic and Indian Oceans , where they provide habitable and agricultural land for hundreds of thousands of people...
  
  , a small, low island
• Chroma key
  Chroma key
  Chroma key compositing is a technique for compositing two images together. A color range in the top layer is made transparent, revealing another image behind. The chroma keying technique is commonly used in video production and post-production...
  
  , a method to superimpose several video layers using areas of a defined color as a mask
• Churchkey, various kinds of bottle and can openers
• Clef
  Clef
  A clef is a musical symbol used to indicate the pitch of written notes. Placed on one of the lines at the beginning of the staff, it indicates the name and pitch of the notes on that line. This line serves as a reference point by which the names of the notes on any other line or space of the staff...
  
   (from the French for "key"), the symbol that assigns note names to the lines and spaces of the musical staff
• Greek key pattern, a meander pattern
• House of Keys
  House of Keys
  The House of Keys is the directly elected lower branch of Tynwald, the parliament of the Isle of Man, the other branch being the Legislative Council....
  
  , the directly elected lower branch of Tynwald, the parliament of the Isle of Man
• Identification key
  Identification key
  In biology, an identification key is a printed or computer-aided device that aids the identification of biological entities, such as plants, animals, fossils, microorganisms, and pollen grains...
  
  , a method of deducing the correct species assignment of a living thing
• KeyBank, a bank headquartered in the Key Tower in Cleveland, Ohio
• Key (basketball)
  Key (basketball)
  The key, officially referred to as the free throw lane by the National Basketball Association and the National Collegiate Athletic Association , the restricted area by the international governing body FIBA, and colloquially as the shaded lane and the paint, is an area in a basketball court...
  
  , also known as the shaded lane in a basketball court
• Keychain
  Keychain
  A keychain or key chain is a small chain, usually made from metal or plastic, that connects a small item to a keyring. The length of a keychain allows an item to be used more easily than if connected directly to a keyring...
  
  , small chain that connects a small item to a keyring
• Key (chart), a guide to colours and symbols used in a data chart, graph, plot or diagram
• Key Club
  Key Club
  Key Club International is the oldest and largest service program for high school students. It is a student-led organization whose goal is to teach leadership through serving others. Key Club International is a part of the Kiwanis International family of service-leadership programs...
  
  , a worldwide student service organization
• Key color (typically black), in the CMYK color model
  CMYK color model
  The CMYK color model is a subtractive color model, used in color printing, and is also used to describe the printing process itself. CMYK refers to the four inks used in some color printing: cyan, magenta, yellow, and key...
  
  
• Key (company)
  Key (company)
  Key is a Japanese visual novel studio which formed on July 21, 1998 as a brand under the publisher Visual Art's and is located in Kita, Osaka, Japan. Key released their debut visual novel Kanon in June 1999, which combined an elaborate storyline, an up-to-date anime-style drawing style, and a...
  
  , a Japanese visual novel studio
• Key frame
  Key frame
  A key frame in animation and filmmaking is a drawing that defines the starting and ending points of any smooth transition. They are called "frames" because their position in time is measured in frames on a strip of film...
  
  , a frame made by an animator from which other frames are derived
• Key light
  Key light
  The key light is the first and usually most important light that a photographer, cinematographer, lighting cameraman, or other scene composer will use in a lighting setup. The purpose of the key light is to highlight the form and dimension of the subject. The key light is not a rigid requirement;...
  
  , the primary light source that illuminates an image or scene
• Keyline
  Keyline
  A keyline, in graphic design, is a boundary line that separates color and monochromatic areas or differently colored areas of printing on a given page or other printed piece. The line itself, usually consisting of a black border, provides an area in which lighter colors can be printed with slight...
  
  , a dark line separating color elements in four-color printing
• Key (map), a guide to a map's symbology
• Key or legend, an explanation of the symbols and colours used in a diagram
  Diagram
  A diagram is a two-dimensional geometric symbolic representation of information according to some visualization technique. Sometimes, the technique uses a three-dimensional visualization which is then projected onto the two-dimensional surface...
  
  
• Key plate
  Key plate
  In printing, a key plate is the plate which prints the detail in an image.When printing color images by combining multiple colors of inks, the colored inks usually do not contain much image detail...
  
  , a plate which prints the detail in an image, often using the color black
• Keys, a truce term used in western Scotland
• Keystone (architecture)
  Keystone (architecture)
  A keystone is the wedge-shaped stone piece at the apex of a masonry vault or arch, which is the final piece placed during construction and locks all the stones into position, allowing the arch to bear weight. This makes a keystone very important structurally...
  
  , the stone at the apex of an arch that holds the arch in place
• Kirby's Epic Yarn
  Kirby's Epic Yarn
  Kirby's Epic Yarn, known in Japan as , is a platform video game developed for the Wii video game console by Good-Feel and HAL Laboratory, and published by Nintendo. It is the tenth installment of the Kirby video game series....
  
  , a 2010 game by Nintendo
• Quay
• Samara (fruit)
  Samara (fruit)
  A samara is a type of fruit in which a flattened wing of fibrous, papery tissue develops from the ovary wall. A samara is a simple dry fruit and indehiscent . It is a winged achene...
  
   or key, a type of fruit in which a flattened wing of fibrous, papery tissue develops from the ovary wall
• Skeleton key
  Skeleton Key
  Skeleton Key is a rock band based in New York City. The band is the brainchild of bassist and singer Erik Sanko, who is the only constant member of the band...
  
   or Master key, a key altered to bypass wards placed inside a lock
• Subkey
  Subkey
  Subkey can refer to:* A hard-coded parameter in a key schedule* A key in OpenPGP that is bound by a master key...
  
  
• Telegraph key
  Telegraph key
  Telegraph key is a general term for any switching device used primarily to send Morse code. Similar keys are used for all forms of manual telegraphy, such as in electrical telegraph and radio telegraphy.- Types of keys :...
  
  , the button used by a telegraph operator
• The Key (disambiguation)