咸知 (xián zhī) is a literary and formal adverb meaning 'all know' or 'universally known.' The character 咸 (xián) is an archaic word meaning 'all' or 'every,' rarely used in modern spoken Chinese except in fixed expressions or classical contexts. 知 (zhī) means 'to know.' Together, 咸知 conveys collective awareness — not just that many people know something, but that it is widely, even inevitably, recognized. It often appears in written language: official announcements, historical texts, formal speeches, or journalistic commentary where emphasis is placed on shared understanding or common knowledge.

This term carries a tone of authority and inevitability — suggesting the fact is so obvious or well-established that no one could reasonably be unaware of it. It is not used in casual conversation; learners should treat it as a stylistic marker of formality and gravitas, similar to English phrases like 'it goes without saying' or 'it is universally acknowledged.' While grammatically functioning as an adverb, it typically modifies the entire clause rather than a single verb.