co-

co-

is a prefix of Latin origin, and is used to form words that include the meaning ‘together, in common’. Spelling practice varies with regard to use of a hyphen: some words (especially when the second element begins with a vowel) include it, whereas others are written as one word. The diaeresis (ö) that formerly punctuated words as in coöperate, is now largely disused. Recommended spellings are as follows:

coagulate / cofactor / co-opt

coalition / cogeneration / coordinate

co-author (noun and verb) / cohabit / co-parent

cohere / co-partner

coaxial / co-host / co-pilot

co-determination / coincide / co-respondent (in divorce case)

co-driver / coition

co-education / co-latitude / co-signatory (to an agreement etc.)

coefficient / co-occur

coequal / co-occurrence / co-star

coeval / co-op / co-worker

coexist / cooperate / uncooperative

coexistent / cooperation / uncoordinated

coextensive / cooperative