Both 才 (cái) and 就 (jiù) are adverbs that have to do with expressing time, and they are both placed in front of the verb. However, they both have a different tone and feel, and they express different lengths of time.


才 expresses that the speaker thinks that the the time that passed since the action takes place was a long time. Sometimes it expresses anxiety, impatience, anger etc.
Structure

Examples

Tā chí dào le bàn ɡè xiǎo shí cái lái 。
他 迟到 了 半 个 小时 才 来。
He came a half an hour late.


就 expresses that the speaker thinks that the time since the action happened is short, and it has a surprise, unexpectedness, or even sometimes regret.

Structure

Examples

Nǐ men zhè me zǎo jiù xià bān le?
你们 这么 早 就 下班 了?
Why are you guys leaving work so early?

就 is used to express earliness
就 indicates that something has occurred earlier than expected

Structure

Examples

Tā xià wǔ sì diǎn jiù chī wǎn fàn 。
他 下午 四点 就 吃 晚饭。
He ate dinner at four in the afternoon.