The tail test:

Monkeys and apes belong to a group of animals called primates.

Humans are primates, too. Other non-human primates include tarsiers, lemurs, and lorises.

Monkeys and apes are different in many ways. But an easy way to tell them apart is to check for a tail.

*The Barbary macaque is a tailless monkey that is an exception to this rule.

Now you know!