就/才
jiù / cái
就 and 才 don't measure time. They measure your expectations
The picture A ruler of time with one tick on it: the point where you expected things to land. Finish before that tick and you get 就; land past it and you get 才.
Where the picture shows up in 就/才
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earlier than expected
他七点就到了。
tā qī diǎn jiù dào le
He was already there at seven.
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later than expected
他十点才到。
tā shí diǎn cái dào
He didn't get in until ten.
-
less effort than expected
我看一遍就记住了。
wǒ kàn yí biàn jiù jì zhù le
One read-through and I had it memorised.
-
more effort than expected
我看了三遍才记住。
wǒ kàn le sān biàn cái jì zhù
It took me three read-throughs to memorise it.
-
no gap between condition and result
你来了我就走。
nǐ lái le wǒ jiù zǒu
Once you're here, I'll be off.
才 cannot stand here; 才 attaches only to what has already happened.