A2 one person or thing in a group that has already been talked about: I’ve just made some cakes. Do you want one? Chris is the one with glasses.
› formal any person in general: One should respect one’s parents.
one by one › separately, one after the other: They entered the room one by one.
one after another (also one after the other) › first one, then another, then another, and so on: One after another, they left the room. She ate the chocolates one after the other until the box was finished.