Verb/Clause + 时
The noun 时 (shí) means "time" or "when" and functions as a temporal marker indicating the moment at which something happens. It often appears at the end of a time clause to mean "when" or "at the time of," as in 工作时 (when working).
开车时不要看手机。
Kāichē shí bùyào kàn shǒujī.
Don't look at your phone while driving.
考试时请保持安静。
Kǎoshì shí qǐng bǎochí ānjìng.
Please remain quiet during the exam.
吃饭时他突然接到了一个电话。
Chīfàn shí tā tūrán jiēdào le yī ge diànhuà.
He suddenly received a phone call while eating.