Meaning of CO- in English

co- /kəʊ $ koʊ/ BrE AmE prefix

[ Language: Latin ; Origin: 'together, with' , from com- ; ⇨ COM- ]

1 . together with:

to coexist (=exist together or at the same time)

coeducation (=with boys and girls together)

2 . doing something with someone else as an equal or with less responsibility:

my co-author (=someone who wrote the book with me)

the co-pilot (=someone who helps a pilot)

Longman Dictionary of Contemporary English.      Longman - Словарь современного английского языка.