Wiktionary
tell the difference
vb. To differentiate similar things.
Usage examples of "tell the difference".
She could tell the difference when she watched herself in a mirror, see the slight hesitation when the left side of her mouth moved, hear the occasionally slurred words that hesitation produced, even as she felt the skewed sensitivity when the wind kissed her cheek.
None of you humans will be able to tell the difference-I beg your pardon.
Anyone can tell the difference between a Nadrak and a Thull or a Thull and a Mallorean, but Murgos and Grolims are so much alike that you can't tell them apart.