tell apart

There were forty scholars: squirmy, grimy little things that I found it hard to tell apart at first.

All three were well over six feet, and Hjalmar stood head and shoulders over his brothers, whom I never learned to tell apart.

This is the work of some six or seven writers, whose hands are sometimes hard to tell apart.

Far, far above us the monster mountains nuzzled among the clouds till cloud and mountain were hard to tell apart.