分辨 means to distinguish or tell apart things that are similar or mixed, often using senses or reasoning. It is very close to 辨别 (biàn bié), but 辨别 emphasizes careful observation or discernment, while 鉴别 (jiàn bié) is more formal and implies expert examination (e.g., authenticating an artwork). 区分 (qū fēn) focuses on drawing a clear boundary between categories.