As soon as… with 一…就…

Structure 一 + action 1 + 就 + action 2

一…就… (yī… jiù…) chains two closely linked events: "as soon as A (happens), (right away) B". 我一回家就睡觉 = "as soon as I get home, I go to sleep". It also expresses an automatic pattern: 一到夏天就很热 = "as soon as summer comes, it gets hot". 一 goes before the first action; 就 before the second.

Examples

我wǒ一yī回huí家jiā就jiù睡shuì觉jiào。
As soon as I get home, I go to sleep.
他tā一yī下xià课kè就jiù走zǒu了le。
He left as soon as class ended.
一yī到dào夏xià天tiān就jiù很hěn热rè。
As soon as summer comes, it gets hot.

Levels are indicative: they follow the standard Chinese Grammar Wiki (AllSet Learning) progression, not an official HSK 3.0 mapping. We never assign levels by eye.

This point and the other 370, with audio on every example, inside Wanyu.