구별해요 · 구별했어요 · 구별할 거예요 · 구별하세요
to distinguish, tell apart
Example
쌍둥이라서 두 사람을 구별하기가 어려워요.
They're twins, so it's hard to tell them apart.
Word parts
구 divide+별 separate
Literally 'divide and separate'.
Good to know
구별하다 is telling things apart by their differences; 구분하다 is sorting things into groups.