How to use 当…的时候
当 + Event / Situation + (的时候 / 时)，Main Clause
当 introduces the occasion or situation in which the main event takes place. The time clause can describe an ongoing state, a particular event, or a recurring trigger. 的时候 often closes it, while 时 provides a shorter alternative. The following clause explains what happens at that time or under those temporal circumstances.
The main and subordinate clauses can have different subjects, so name them clearly when needed. 就 often introduces a prompt reaction, but it is not part of every 当 sentence. In suitable contexts the closing time expression can be omitted. The construction does not specify past or future on its own; the events and surrounding time information supply that interpretation.
Examples with pinyin and English
当我有自行车的时候，大家都开始骑电动车了。
When I got a bike, everyone started riding electric ones.
当我看到这张照片，我就想起了你。
When I saw this photo, I immediately thought of you.
当弟弟肚子饿的时候，他就会哭得很大声。
When my little brother is hungry, he will cry loudly.
当深颜色和浅颜色的衣服放在一起洗时，浅颜色的衣服会染色。
When washing dark and light colors together, the light-colored clothes will become dyed.
What to remember
- 当 opens the time clause.
- 的时候 or 时 can close that clause.
- 就 can highlight an immediate reaction.
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Source and editorial notes
Explanation rewritten for Laowai. Examples are adapted from the Laowai English grammar curriculum, with editorial corrections where needed. The original curriculum credits AllSet Learning’s Chinese Grammar Wiki as used with permission. Read the retained source credits.
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