CO or variants may refer to:

Chemistry

Carbon monoxide Carbon monoxide (chemical formula CO) is a poisonous, flammable gas that is colorless, odorless, tasteless, and slightly less dense than air. Carbon monoxide consists of one carbon atom and one oxygen atom connected by a triple bond. It is the si ...

(CO), a colorless, odorless, and tasteless gas *

Carbonyl group In organic chemistry, a carbonyl group is a functional group with the formula , composed of a carbon atom double-bonded to an oxygen atom, and it is divalent at the C atom. It is common to several classes of organic compounds (such as aldehydes ...

, composed of a carbon atom double-bonded to an oxygen atom: C=O *

Cobalt Cobalt is a chemical element; it has Symbol (chemistry), symbol Co and atomic number 27. As with nickel, cobalt is found in the Earth's crust only in a chemically combined form, save for small deposits found in alloys of natural meteoric iron. ...

, 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 A telephone exchange, telephone switch, or central office is a central component of a telecommunications system in the public switched telephone network (PSTN) or in large enterprises. It facilitates the establishment of communication circuits ...

, 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 * 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 Colombia, officially the Republic of Colombia, is a country primarily located in South America with Insular region of Colombia, insular regions in North America. The Colombian mainland is bordered by the Caribbean Sea to the north, Venezuel ...

, ISO 3166-1 country code CO *

Colorado Colorado is a U.S. state, state in the Western United States. It is one of the Mountain states, sharing the Four Corners region with Arizona, New Mexico, and Utah. It is also bordered by Wyoming to the north, Nebraska to the northeast, Kansas ...

, United States postal abbreviation CO *

Counties of Ireland The counties of Ireland (Irish language, Irish: ) are historic administrative divisions of the island. They began as Normans in Ireland, Norman structures, and as the powers exercised by the Cambro-Norman barons and the Old English (Ireland), ...

, abbreviated Co.

Ranks and titles

* C.O., post-nominal initials of members of the congregation of the

Oratory of Saint Philip Neri The Confederation of Oratories of Saint Philip Neri (), abbreviated C.O. and commonly known as the Oratorians, is a Catholic Church, Catholic society of apostolic life of pontifical right for men (priests and Religious brother, religious brot ...

* C/O, cadet officer ranks of the Junior Reserve Officers' Training Corps *

Commanding officer The commanding officer (CO) or commander, or sometimes, if the incumbent is a general officer, commanding general (CG), is the officer in command of a military unit. The commanding officer has ultimate authority over the unit, and is usually give ...

(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 A conscientious objector is an "individual who has claimed the right to refuse to perform military service" on the grounds of freedom of conscience or religion. The term has also been extended to objecting to working for the military–indu ...

Transportation

Chemins de fer Orientaux The Chemins de fer Orientaux (English: Oriental Railway; or ''İstanbul-Viyana Demiryolu'') (reporting mark: CO) was an Ottoman Empire, Ottoman railway company operating in Rumelia (the European part of the Ottoman Empire, corresponding to the ...

(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 Continental Airlines (simply known as Continental) was a major airline in the United States that operated from 1934 until it merged with United Airlines in 2012. It had ownership interests and brand partnerships with several carriers. Continen ...

(IATA airline designator CO, 1937-2012), an American airline

Other uses

* co-, an

English prefix English prefixes are affixes (i.e., bound morphemes that provide lexical meaning) that are added before either simple Root (linguistics), roots or complex ''bases'' (or ''operands'') consisting of (a) a root and other affixes, (b) multiple roots, ...

meaning coming together *

Cardiac output In cardiac physiology, cardiac output (CO), also known as heart output and often denoted by the symbols Q, \dot Q, or \dot Q_ , edited by Catherine E. Williamson, Phillip Bennett is the volumetric flow rate of the heart's pumping output: tha ...

(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 A company, abbreviated as co., is a Legal personality, legal entity representing an association of legal people, whether Natural person, natural, Juridical person, juridical or a mixture of both, with a specific objective. Company members ...

, abbreviated co. *

Corsican language Corsican (, , or , ) is a Romance languages, Romance language consisting of the Dialect continuum, continuum of the Tuscan dialect, Tuscan Italo-Dalmatian languages, Italo-Dalmatian dialects spoken on the Mediterranean island of Corsica, a Singl ...

, ISO 639-1 language code co * , a Unicode character in the

Letterlike Symbols Letterlike Symbols is a Unicode block containing 80 characters which are constructed mainly from the glyphs of one or more letters. In addition to this block, Unicode includes full styled mathematical alphabets, although Unicode does not exp ...

block * c/o, former name of Gerhardsen Gerner, an art gallery in Berlin