which is which


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which is which

What particular one is what particular one, or what is the difference between different ones. For example, These twins look so much alike I can't tell which is which, or Both our raincoats are tan; do you know which is which? This idiom was first recorded about 1412.

ˌwhich is ˈwhich

used to talk about distinguishing one person or thing from another: The twins are so alike I can’t tell which is which.