之后 (zhī hòu) is a preposition meaning 'after' in terms of time — it marks a point in time that follows another event or moment. Literally, 之 means 'of' or serves as a possessive/connecting particle, and 后 means 'behind' or 'after'; together, they form a fixed two-character expression indicating temporal sequence. It always follows a noun or time phrase (e.g., 星期一之后, 会议之后, 三年之后) and cannot stand alone.

This word is neutral in register and widely used in both spoken and written Chinese — from casual conversation to formal reports. Unlike the verb 后来 (hòulái, 'later'), 之后 is strictly relational: it must attach to a specific preceding time or event. It does not imply duration or change of state; it simply denotes what happens *following* a named reference point. Learners often confuse it with 以后 (yǐhòu), which is more flexible and can mean 'from now on' or 'in the future' without requiring an explicit prior event.