厘清 is a formal, transitive verb meaning 'to clarify thoroughly' or 'to sort out clearly'. It combines 厘 (lí), which historically means 'to examine carefully' or 'to investigate', and 清 (qīng), meaning 'clear', 'distinct', or 'pure'. Together, they convey the idea of methodically examining something complex—such as responsibilities, facts, relationships, or logical steps—until every element is understood and differentiated. The word implies active mental effort and precision, not just surface-level understanding.

It’s commonly used in academic, professional, and administrative contexts—for example, when untangling overlapping duties in a team, verifying conflicting reports, or defining ambiguous terms in a contract. While it can appear in spoken language, it’s more frequent in writing and formal speech. Unlike simpler verbs like 弄清楚 (nòng qīngchu), 厘清 carries a stronger connotation of systematic analysis and intellectual rigor.