‘须知’ literally means ‘must know’ — combining 须 (xū), meaning ‘must’ or ‘necessary’, and 知 (zhī), meaning ‘to know’. As a noun, it refers to essential, practical information that people need to understand before doing something, especially in official, instructional, or procedural contexts. It often appears in notices, handbooks, or orientation materials.

This term carries a formal, slightly authoritative tone and is commonly used in public announcements, school guidelines, travel advisories, or workplace onboarding documents. While it sounds serious, it’s not overly stiff — native speakers use it naturally when emphasizing non-negotiable basics. Unlike casual phrases like ‘important tips’, 须知 implies that ignoring the information could lead to problems or violations of rules.