Level 3 · Intermediate
As soon as: 一…就…
Subj. + 一 + Verb A，(Subj.) + 就 + Verb B
一…就… chains two actions with zero gap: the moment A happens, B follows. 我一到家就给你打电话 "the second I get home, I'll call you". 一 sits before the first verb, 就 before the second.
It also describes reliable habits and reactions: 她一累就想睡觉 "whenever she's tired, she wants to sleep". Whatever you do, don't drop the 就 — 一 can't carry the pattern alone.
Examples
我一到家就给你打电话。
我一到家就給你打電話。
wǒ yī dào jiā jiù gěi nǐ dǎ diàn huà
I'll call you as soon as I get home.
他一下课就回家了。
他一下課就回家了。
tā yī xià kè jiù huí jiā le
He went home as soon as class ended.
我一看见他就想笑。
我一看見他就想笑。
wǒ yī kàn jiàn tā jiù xiǎng xiào
As soon as I see him, I want to laugh.
她一累就想睡觉。
她一累就想睡覺。
tā yī lèi jiù xiǎng shuì jiào
Whenever she's tired, she wants to sleep.
Common mistakes
✗ 我一到家，给你打电话。
✓ 我一到家就给你打电话。
一 needs its partner 就 before the second verb.
Related grammar points
See it in a story
Read this pattern in context: An Evening Alone · The Boss’ Praise — free graded stories with tap-to-reveal pinyin and translations.
