A CD or compact disc 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, a galaxy morphology classification

Biology, ecology, and medicine

* Coeliac disease, 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, 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 *

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), a command line command to change the current working directory in operating systems * continuous delivery, a software development design practice * continuous deployment, 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, symbol Cd, a chemical element * Candela or cd, a unit of light intensity * -CD, the North American call sign 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 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, by post-nominal letters * Centre Democrats (Denmark), a Danish former political party * Centre Democrats (Netherlands), a former political party of the Netherlands * '' Centro Democratico'', 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, an intergovernmental organization of democracies and democratizing countries * Conference on Disarmament, 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 or ČD, a railway operator of the Czech Republic * Commander of the Order of Distinction, a rank in the Jamaican Orders of Societies of Honour

Places

* Central District, Seattle, a district in Seattle * Democratic Republic of the Congo, 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 Turkish postal addresses are usually written with the name of the main street, minor street, apartment block name, apartment number, then finally Provinces of Turkey and five figure zipcode.Tom Brosnahan ''Turkey: a travel survival kit'' 4th ed ...

, 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 __NOTOC__ Year 400 ( CD) was a leap year starting on Sunday (link will display the full calendar) of the Julian calendar. In the Roman Empire, it was known as the Year of the Consulship of Stilicho and Aurelianus (or, less frequently, year 11 ...

(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 The Damascus Document is an ancient Hebrew text known from both the Cairo Geniza and the Dead Sea Scrolls.Philip R. Davies, "Damascus Document", in Eric M. Meyers (ed.), ''The Oxford Encyclopedia of Archaeology in the Near East'' (Oxford Univer ...

or Damascus Document, a text found among the Dead Sea Scrolls * Committee Draft, a status in the International Organization for Standardization *

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 (IATA code) * Sega Mega-CD ** Sonic CD