A CD or compact disc is a thin plastic silvery disc for audio recordings.

CD, C/D, Cd or cd may also refer to:

• CD-ROM, the same technology used for computer data
• Certificate of deposit, bank account in the United States with a fixed maturity date

In science and technology:

• cd (command), a command line command to change the current working directory in operating systems
• .cd, the Internet domain of the Democratic Republic of the Congo
• Cadmium or Cd, the chemical element
• Candela or cd, a unit of light intensity
• Circular dichroism, a form of spectroscopy
• Cluster of differentiation, a protocol used for the identification and investigation of cell surface molecules present on white blood cells
• Cordoba Durchmusterung, a star catalogue of the southern sky
• Drag coefficient or c_d, a dimensionless quantity that is used to quantify the drag or resistance of an object in a fluid environment
• Type-cD galaxy, a galaxy morphology classification
• -CD, the North American call sign suffix for Class A low-power television stations operating with digital signals

In politics:

• Cairo Damascus or Damascus Document, a text found among the Dead Sea Scrolls
• Canadian Forces Decoration, a Canadian award bestowed upon members of the Canadian Forces who have completed twelve years of military service
• Centre Democrats (Denmark), a former Danish political party
• Centre Democrats (Netherlands), a former political party of the Netherlands
• Community of Democracies, an intergovernmental organization of democracies and democratizing countries
• Conference on Disarmament, a forum established by the international community to negotiate multilateral arms control and disarmament agreements
• Corps Diplomatique, the collective body of foreign diplomats accredited to a particular country or body

In other uses:

• 400 (number), or CD in Roman numerals
• Geely CD, a coupe automobile from Geely Automobile
• České Dráhy or ČD, the main railway operator of the Czech Republic
• Commander of the Order of Distinction, a rank in the Jamaican Order of Distinction
• Companion dog (title), a title offered by the American Kennel Club for dog obedience
• "CD", a song by T2
• Civil Defense

See also[link]

• Conservation Dependent or LR/cd, an IUCN category assigned to species or lower taxa which were dependent on conservation efforts to prevent the taxon becoming threatened with extinction

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