A person who performs or acts together with another person in a shared role or action.
From co- (together) + actor (from Latin agere, to act). The noun form emerged in theater and drama to identify someone who shares performance duties with a colleague.
Hollywood studios started using 'co-star' instead of 'coenactor' because it's catchier, but this older term shows how specific theatrical vocabulary was before the film industry simplified it for audiences.
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