WHICH IS WHICH

{n. phr.} Which is one person or thing and which is the other; one from another; what the difference is between different ones; what the name of each one is. * /Joe's coat and mine are so nearly alike that I can't tell which is which./ * /Mr. Hadley hadn't seen his friend's daughters in such a long time that he couldn't remember which was which./ Compare: WHAT'S WHAT, WHO'S WHO.