才不……呢: certainly not! (我才不去呢)
【六12】语气副词 / adverbs
Tone colorsā tone 1á tone 2ǎ tone 3à tone 4a neutral
才 before a negation (不 or 没), usually closed by a sentence-final 呢, is a flat "certainly not": it rejects a suggestion or an assumption outright. 我才不去呢 means "there's no way I'm going".
Three uses: refusing (我才不要父母的钱呢), denying (with 没 for the past: 谁说的？我才没说过呢), and throwing an accusation back (你才傻呢! "you're the silly one"), where 才 even goes with a positive word. This is not the 才 of "only then" (他八点才到, level 2): here 才 has nothing to do with time, it carries pure attitude.
Register: spoken, lively, a little defiant or sulky, perfectly natural among friends, family and close colleagues. To a boss or a stranger it is far too blunt: soften it with 我不太想去 or 恐怕不行.
Examples
我才不去呢！
Wǒ cái bú qù ne!I'm certainly not going!
谁说的？我才没说过呢！
Shéi shuō de? Wǒ cái méi shuō guo ne!Who said that? I never said any such thing!
这么冷的天，我才不出门呢，我要在家看电影。
Zhème lěng de tiān, wǒ cái bù chūmén ne, wǒ yào zài jiā kàn diànyǐng.In this cold? No way I'm going out; I'm staying in to watch a film.
我才不要父母的钱呢，我要自己赚钱。
Wǒ cái bú yào fùmǔ de qián ne, wǒ yào zìjǐ zhuànqián.I want none of my parents' money; I'll earn my own.
你才傻呢，我是在帮你！
Nǐ cái shǎ ne, wǒ shì zài bāng nǐ!You're the silly one! I'm trying to help you!
他说我胖？他自己才该减肥呢！
Tā shuō wǒ pàng? Tā zìjǐ cái gāi jiǎnféi ne!He says I'm fat? He's the one who ought to go on a diet!
Common mistakes
✗ 我不才要钱呢 → ✓ 我才不要钱呢 (才 stands before the negation, never after it).
✗ 经理，我才不去呢。 → ✓ 经理，我不太想去。 (to a superior the tone is far too defiant).
✗ 我才不去过呢 → ✓ 我才没去过呢 (for the past, 过 and 了 go with 没, not 不).