A CD or

compact disc The compact disc (CD) is a Digital media, digital optical disc data storage format that was co-developed by Philips and Sony to store and play digital audio recordings. In August 1982, the first compact disc was manufactured. It was then rele ...

is a thin plastic silvery disc for audio recordings. CD or cd may also refer to:

Science and technology

Astronomy and cosmology

Cordoba Durchmusterung In astronomy, Durchmusterung or Bonner Durchmusterung (BD) is an astrometric star catalogue of the whole sky, compiled by the Bonn Observatory in Germany from 1859 to 1903. The name comes from ('run-through examination'), a German word used for ...

, a star catalog of the southern sky *

Cosmological decade A cosmological decade (CÐ) is a division of the lifetime of the cosmos. The divisions are logarithmic in size, with base 10. Each successive cosmological decade represents a ten-fold increase in the total age of the universe. As expressed in l ...

or CÐ, a unit of time *

Type-cD galaxy The type-cD galaxy (also cD-type galaxy, cD galaxy) is a galaxy morphology classification, a subtype of type-D giant elliptical galaxy. Characterized by a large halo of stars, they can be found near the centres of some rich galaxy clusters. They ...

, a galaxy morphology classification

Biology, ecology, and medicine

Coeliac disease Coeliac disease (British English) or celiac disease (American English) is a long-term autoimmune disorder, primarily affecting the small intestine, where individuals develop intolerance to gluten, present in foods such as wheat, rye and barle ...

, long term autoimmune disorder causing intolerance to gluten *

Conduct disorder Conduct disorder (CD) is a mental disorder diagnosed in childhood or adolescence that presents itself through a repetitive and persistent pattern of behavior that includes theft, lies, physical violence that may lead to destruction, and reckles ...

, a psychological disorder *

Conservation Dependent A conservation-dependent species is a species which has been categorised as "Conservation Dependent" ("LR/cd") by the International Union for Conservation of Nature (IUCN), i.e. as dependent on conservation efforts to prevent it from becoming e ...

or LR/cd, an IUCN category *

Cluster of differentiation The cluster of differentiation (also known as cluster of designation or classification determinant and often abbreviated as CD) is a protocol used for the identification and investigation of cell surface molecules providing targets for immunophen ...

, a protocol used for the identification of cell surface molecules on white blood cells *

Crohn's disease Crohn's disease is a type of inflammatory bowel disease (IBD) that may affect any segment of the gastrointestinal tract. Symptoms often include abdominal pain, diarrhea (which may be bloody if inflammation is severe), fever, abdominal distension ...

Chlordane Chlordane, or chlordan, is an organochlorine compound that was used as a pesticide. It is a white solid. In the United States, chlordane was used for termite-treatment of approximately 30 million homes until it was banned in 1988. Chlordane was b ...

Communicable disease An infection is the invasion of tissues by pathogens, their multiplication, and the reaction of host tissues to the infectious agent and the toxins they produce. An infectious disease, also known as a transmissible disease or communicable dise ...

Computing

CD-ROM A CD-ROM (, compact disc read-only memory) is a type of read-only memory consisting of a pre-pressed optical compact disc that contains data. Computers can read—but not write or erase—CD-ROMs. Some CDs, called enhanced CDs, hold both comput ...

, compact disc technology applied for use in computer data *

cd (command) The command, also known as (change directory), is a command-line shell command used to change the current working directory in various operating systems. It can be used in shell scripts and batch files. Implementations The command has been ...

, a command line command to change the current working directory in operating systems *

continuous delivery Continuous delivery (CD) is a software engineering approach in which teams produce software in short cycles, ensuring that the software can be reliably released at any time and, following a pipeline through a "production-like environment", withou ...

, a software development design practice *

continuous deployment Continuous deployment (CD) is a software engineering approach in which software functionalities are delivered frequently and through automated deployments. Continuous deployment contrasts with continuous delivery (also abbreviated CD), a similar ...

, a software development design practice * collision detection,

CSMA/CD Carrier-sense multiple access with collision detection (CSMA/CD) is a medium access control (MAC) method used most notably in early Ethernet technology for local area networking. It uses carrier-sensing to defer transmissions until no other statio ...

Mathematics

cd (elliptic function) In mathematics, the Jacobi elliptic functions are a set of basic elliptic functions. They are found in the description of the motion of a pendulum (see also pendulum (mathematics)), as well as in the design of electronic elliptic filters. While tri ...

, one of Jacobi's elliptic functions

Other uses in science and technology

Cadmium Cadmium is a chemical element with the symbol Cd and atomic number 48. This soft, silvery-white metal is chemically similar to the two other stable metals in group 12, zinc and mercury. Like zinc, it demonstrates oxidation state +2 in most of ...

, symbol Cd, a chemical element *

Candela The candela ( or ; symbol: cd) is the unit of luminous intensity in the International System of Units (SI). It measures luminous power per unit solid angle emitted by a light source in a particular direction. Luminous intensity is analogous to ...

or cd, a unit of light intensity * -CD, the

North American call sign Call signs are frequently still used by North American broadcast stations, in addition to amateur radio and other international radio stations that continue to identify by call signs around the world. Each country has a different set of pattern ...

suffix for Class A low-power television stations operating with digital signals * Circular dichroism, a form of spectroscopy *

Critical Dimension In the renormalization group analysis of phase transitions in physics, a critical dimension is the dimensionality of space at which the character of the phase transition changes. Below the lower critical dimension there is no phase transition. ...

, the minimum feature size that a projection system can print in photolithography *

Drag coefficient In fluid dynamics, the drag coefficient (commonly denoted as: c_\mathrm, c_x or c_) is a dimensionless quantity that is used to quantify the drag or resistance of an object in a fluid environment, such as air or water. It is used in the drag equ ...

or ''c_d'', a dimensionless quantity used to quantify the drag of an object in a fluid *

Cluster decay Cluster decay, also named heavy particle radioactivity or heavy ion radioactivity, is a rare type of nuclear decay in which an atomic nucleus emits a small "cluster" of neutrons and protons, more than in an alpha particle, but less than a typic ...

, a rare mode of nuclear decay

Businesses and organizations

Government, military, and political

Canadian Forces Decoration The Canadian Forces' Decoration (post-nominal letters "CD") is a Canadian award bestowed upon members of the Canadian Armed Forces who have completed twelve years of military service, with certain conditions. By convention, it is also given to t ...

, by post-nominal letters *

Centre Democrats (Denmark) The Centre Democrats ( da, Centrum-Demokraterne, CD) were a Danish political party. History The party was formed in 1973 by Erhard Jakobsen, a former MP and mayor of Gladsaxe, as a centrist splinter group from the Danish Social Democrats. It p ...

, a Danish former political party *

Centre Democrats (Netherlands) The Centre Democrats ( nl, Centrum Democraten, CD) was a political party in the Netherlands. Founded in 1984 by members who split out from the Centre Party (CP), the Centre Democrats was joined one month later by the only CP Member of Parliamen ...

, a former political party of the Netherlands * ''

Centro Democratico Democratic Centre ( it, Centro Democratico, CD) is a centrist, Christian leftist and social-liberal political party in Italy. Most of its members, including its leader Bruno Tabacci, are former Christian Democrats. Since its beginnings, the C ...

'', a political party in Italy *

Christian democracy Christian democracy (sometimes named Centrist democracy) is a political ideology that emerged in 19th-century Europe under the influence of Catholic social teaching and neo-Calvinism. It was conceived as a combination of modern democratic ...

, a political ideology *

Civil defense Civil defense ( en, region=gb, civil defence) or civil protection is an effort to protect the citizens of a state (generally non-combatants) from man-made and natural disasters. It uses the principles of emergency operations: prevention, miti ...

, an effort to protect the citizens of a state from military attack and natural disasters *

Community of Democracies The Community of Democracies (C.O.D), established in 2000, is an intergovernmental coalition of states. Its aim is to bring together governments, civil society and the private sector in the pursuit of the common goal of supporting democratic rul ...

, an intergovernmental organization of democracies and democratizing countries *

Conference on Disarmament The Conference on Disarmament (CD) is a multilateral disarmament forum established by the international community to negotiate arms control and disarmament agreements based at the Palais des Nations in Geneva. The Conference meets annually in ...

, an international forum that negotiates multilateral arms control and disarmament agreements * ''

Corps Diplomatique The diplomatic corps (french: corps diplomatique) is the collective body of foreign diplomats accredited to a particular country or body. The diplomatic corps may, in certain contexts, refer to the collection of accredited heads of mission ( a ...

'', the collective body of foreign diplomats accredited to a particular country or body *

FBI Counterintelligence Division The Counterintelligence Division (CD) is a division of the National Security Branch of the Federal Bureau of Investigation. The division protects the United States against foreign intelligence operations and espionage. It accomplishes its miss ...

, the United States Federal Bureau of Investigation's division responsible for investigating espionage

Other business and organizations

Certificate of deposit A certificate of deposit (CD) is a time deposit, a financial product commonly sold by banks, thrift institutions, and credit unions in the United States. CDs differ from savings accounts in that the CD has a specific, fixed term (often one, th ...

, a bank account in the United States with a fixed maturity date *

České dráhy České dráhy (English: ''Czech Railways''), often shortened to ČD, is the major railway operator in the Czech Republic providing regional and long-distance services. Overview The company was established in 1993, after the dissolution of Cze ...

or ČD, a railway operator of the Czech Republic *

Commander of the Order of Distinction The Order of Distinction is a national order in the Jamaican honours system. It is the sixth in order of precedence of the Orders of Societies of Honour, which were instituted by an Act of Parliament (''The National Honours and Awards Act'') i ...

, a rank in the Jamaican Orders of Societies of Honour

Places

Central District, Seattle The Central Area, commonly called the Central District or The CD,Mary T. HenrySeattle Neighborhoods: Central Area -- Thumbnail History HistoryLink, March 10, 2001. Accessed online 2009-10-19. is a mostly residential district in Seattle located ea ...

, a district in Seattle *

Democratic Republic of the Congo The Democratic Republic of the Congo (french: République démocratique du Congo (RDC), colloquially "La RDC" ), informally Congo-Kinshasa, DR Congo, the DRC, the DROC, or the Congo, and formerly and also colloquially Zaire, is a country in ...

, by ISO 3166-1 alpha-2 country code **

.cd .cd is the Internet country code top-level domain (ccTLD) for the Democratic Republic of the Congo. It was created in 1997 as a replacement for the .zr (Zaire) ccTLD, which was phased out and eventually deleted in 2001. Except for reserved names ...

, the Internet domain of the Democratic Republic of the Congo * cd., abbreviation for caddesi, street, in Turkish

Other uses

400 (number) 400 (four hundred) is the natural number following 399 and preceding 401. Mathematical properties 400 is the square of 20. 400 is the sum of the powers of 7 from 0 to 3, thus making it a repdigit in base 7 (1111). A circle is divided into 4 ...

, written CD in Roman numerals *

205 (number) 205 (two hundred ndfive) is the natural number following 204 and preceding 206. In mathematics 205 is a lucky number, and a Wolstenholme number. On an infinite chessboard, a knight can reach exactly 205 squares within four moves. There are 20 ...

, written CD in hexadecimal * AD 400 (CD), a year of the Common Era * "CD", a song by

T2 (band) T2 were an English progressive rock band, best known for their 1970 album, '' It'll All Work Out in Boomland''. It is generally regarded as an excellent album. Origins T2 evolved from an earlier band, Neon Pearl, which was led by their drumm ...

Geely CD The Geely CD is a 2-door coupé from Chinese manufacturer Geely Automobile. Overview The Chinese name for the Geely CD is the "Geely Zhongguolong" (中国龙), meaning "Chinese Dragon", with the "CD" name based on it. The CD was shown at the Fra ...

, a coupe automobile made by Geely Automobile * Cairo Damascus or Damascus Document, a text found among the Dead Sea Scrolls * Committee Draft, a status in the

International Organization for Standardization The International Organization for Standardization (ISO ) is an international standard development organization composed of representatives from the national standards organizations of member countries. Membership requirements are given in Ar ...

Companion dog (title) The American Kennel Club (AKC) is a registry of purebred dog pedigrees in the United States. In addition to maintaining its pedigree registry, this kennel club also promotes and sanctions events for purebred dogs, including the Westminster Kenn ...

, a title offered to dogs by the American Kennel Club for dog obedience *

Cross-dressing Cross-dressing is the act of wearing clothes usually worn by a different gender. From as early as pre-modern history, cross-dressing has been practiced in order to disguise, comfort, entertain, and self-express oneself. Cross-dressing has play ...

, the act of wearing clothing associated with the opposite sex *

Corendon Dutch Airlines Corendon Dutch Airlines is a Dutch charter and scheduled airline headquartered in Lijnden, Haarlemmermeer. It is a sister company of Corendon Airlines and Corendon Airlines Europe. History Corendon Dutch Airlines is the Dutch branch of the ' ...

(IATA code) *

Sega Mega-CD The Sega CD, released as the in most regions outside North America and Brazil, is a CD-ROM accessory for the Sega Genesis produced by Sega as part of the fourth generation of video game consoles. It was released on December 12, 1991, in Japan, ...

Sonic CD is a 1993 platform game for the Sega CD developed and published by Sega. The story follows Sonic the Hedgehog as he attempts to save an extraterrestrial body, Little Planet, from Doctor Robotnik. Like other '' Sonic'' games, Sonic runs and ...