CO or variants may refer to:

Look up co, -co, c/o, care of, or co- in Wiktionary, the free dictionary.

• 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

• .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)

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

• 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
• Nando Có (born 1973), Bissau-Guinean footballer
• Kenedy Có (born 1998), Bissau-Guinean footballer
• Samuel S. Co, Filipino politician

• 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.

• 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

• 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

• 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
• Company, abbreviated co.
• Corsican language, ISO 639-1 language code co
• ℅, a Unicode character in the Letterlike Symbols block
• c/o, former name of Gerhardsen Gerner, an art gallery in Berlin

• C0 (disambiguation), the letter–number combination
• Care of (disambiguation)
• Co-Co locomotives

This disambiguation page lists articles associated with the title CO.
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