CO or variants may refer to:

Chemistry

  • Carbon monoxide (CO), a colorless, odorless, and tasteless gas
  • Carbonyl group, composed of a carbon atom double-bonded to an oxygen atom: C=O
  • Cobalt, a chemical element, symbol Co

Computing and telecommunications

  • .co (second-level domain), the Internet second-level domain meaning "commercial"
  • .co, the Internet country code top-level domain (ccTLD) for Colombia
  • Commitment ordering (CO), a concurrency control technique for databases
  • Telephone exchange, or central office (CO)

Mathematics

  • Cofunction, or Co, in trigonometry
  • Cuboctahedron, a uniform polyhedron

People

  • Nguyễn Hữu Có (1925–2012), Vietnamese general
  • Conrado Co (born 1940), Filipino badminton player
  • Alfredo Co (born 1949), Filipino Sinologist
  • Atoy Co (born 1951), Filipino actor and basketball coach
  • Leonard Co (1953–2010), Filipino botanist
  • Marivic Co-Pilar (born 1971), Filipino politician
  • Nando Có (born 1973), Bissau-Guinean footballer
  • Kenedy Có (born 1998), Bissau-Guinean footballer
  • Samuel S. Co, Filipino politician

Places

  • CO postcode area, or Colchester postcode area, England
  • Colombia, ISO 3166-1 country code CO
  • Colorado, United States postal abbreviation CO
  • Counties of Ireland, abbreviated Co.

Ranks and titles

  • C.O., post-nominal initials of members of the congregation of the Oratory of Saint Philip Neri
  • C/O, cadet officer ranks of the Junior Reserve Officers' Training Corps
  • Commanding officer (CO), the officer in command of a military unit
  • Contracting Officer (CO or KO), in the U.S. government
  • Correctional officer (CO), an officer whose duty it is to safeguard and promote the welfare of inmates
  • Circle officer (CO), in the Indian government
  • Conscientious objector

Transportation

  • Chemins de fer Orientaux (CO), a former Ottoman railway company
  • Chesapeake and Ohio Railway (C&O or CO), a former American railroad
  • Cobalt Air (IATA airline designator CO, 2016-2018), a Cypriot airline
  • Continental Airlines (IATA airline designator CO, 1937-2012), an American airline

Other uses

  • co-, an English prefix meaning coming together
  • Cardiac output (CO), the volume of blood being pumped by the heart per time unit
  • Castres Olympique, a French rugby club
  • Certificate of occupancy (CO), a legal document
  • Certificate of origin (often abbreviated to C/O or CoO), in international trade
  • Co (Armenian letter)
  • Company, abbreviated co.
  • Corsican language, ISO 639-1 language code co
  • (), a character in the Unicode Letterlike Symbols block, meaning 'care of'
  • c/o, former name of Gerhardsen Gerner, an art gallery in Berlin

See also

  • C0 (disambiguation), the letternumber combination
  • Care of (disambiguation)
  • Cobalt (disambiguation)
  • Co-Co locomotives