时 — when, at the time of

时 (shí) works as a suffix added to a verb or verb phrase to mean "when/while doing X": 吃饭时 (while eating), 上课时 (during class). It is more formal and written than 的时候 (de shíhou), its colloquial equivalent. Both are correct, but 时 appears more in written texts and 的时候 in everyday speech.

时 (shí) works as a suffix added to a verb or verb phrase to mean "when/while doing X": 吃饭时 (while eating), 上课时 (during class). It is more formal and written than 的时候 (de shíhou), its colloquial equivalent. Both are correct, but 时 appears more in written texts and 的时候 in everyday speech.