CO can stand for:

• Carbon monoxide, molecular formula
• Central office, in telecommunications and telephony
• Chesapeake and Ohio Railroad
• Colombia, in various country codes
• Colorado, U.S. postal abbreviation
• Commanding officer, military
• Conscientious objector, military
• Continental Airlines, IATA airline designator
• Collaborative Browsing
• Chinese Orchestra
• Correctional Officer, Correctional Officer
• Conjure One, a Canadian music artist

Co can stand for:

• Cobalt, a ferromagnetic metallic chemical element
• Company (law) (Co.), a general business abbreviation
• Co (ethnicity), an ethnic group in Southeast Asia
• Cowling number, in physics

co can stand for:

• "check out", Revision Control System command

.co can stand for:

• .co, the Internet second-level domain within other country code domains

c/o can stand for:

• "Care of", used to address a letter when the letter must pass through an intermediary

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