不……不……: "no A, no B"
【六53】复句 / complex sentences
Tone colorsā tone 1á tone 2ǎ tone 3à tone 4a neutral
不 A 不 B states a necessary condition in a few syllables: "no A, no B", or "until A happens, B doesn't". 不打不成交: you only strike the deal after having fought. 不见不散: nobody leaves until you have met.
It is a contracted sentence (紧缩复句): two negated clauses are glued together with no connector, and the first is the condition of the second. The logic is that of 只有……才……, in a short, categorical version. Each half can have its own subject: 他不来，我不走; 钱不付清，工人不干活.
This mould belongs to proverbs, slogans, regulations and firm promises (不达标准不休息). The 不 stays a real 不: you cannot swap it for 没. Do not confuse it with 不冷不热 or 不声不响 ("neither… nor…"), where two parallel words describe a state with no condition.
Examples
不见不散！
Bú jiàn bú sàn!Be there, nobody leaves until we've met!
他不来，我不走。
Tā bù lái, wǒ bù zǒu.If he doesn't come, I'm not leaving.
你们两个人真是不打不成交。
Nǐmen liǎng ge rén zhēn shì bù dǎ bù chéngjiāo.You two really had to fight first before you could strike a deal.
钱不付清，工人不干活。
Qián bú fù qīng, gōngrén bú gàn huó.Until the money is paid in full, the workers won't work.
她今天一直在练习，不达到标准不休息。
Tā jīntiān yìzhí zài liànxí, bù dádào biāozhǔn bù xiūxi.She has been practising all day and won't rest until she reaches the standard.
Common mistakes
✗ 没打没成交 → ✓ 不打不成交 (in this proverbial mould it is 不, not 没).
✗ 不散不见 → ✓ 不见不散 (the condition comes first, the consequence second).
✗ reading 不见不散 as "we don't meet, we don't part" → it is a condition: "until we have met, nobody leaves", so you wait for the other person.