fit作形容词
1.和系动词连用，表示“适合，恰当”等。
He isn’t fit for his work. 他不适合做这项工作。
The food isn’t fit to eat. 这食物不好吃。
It”s fir that he should say so. 他那样说是恰当的。
2.和feel或keep等连用，表示精神极好，保持健康等。
Though he is over 70 years old, he feels fit. 尽管他70多岁，但精神头极好。
I hope you are keeping fit. 我希望你能保持健康。
3.口语中常用作状语，表示就要，几乎。
She cried fit to break her heart. 她哭得死去活来
They went on working till they were fit to drop. 他们继续工作，几乎要累倒。
fit作名词
1.前面可以加不定冠词和形容词，表示合身，合身的衣服。
Fit is even more important than color. 合身比颜色更重要。
The coat is a good fit. 这件大衣很合身。
2.表示突然爆发或发病等。
When he made a face, the others burst into a fit of laughter. 他做个鬼脸，大家一阵大笑。
He suddenly fell in a fit while he was walking along the street. 当他在街上漫步时，突然昏倒了。
3.口语中常和give或have连用表示大吃一惊，大发脾气。
That he had passed the exam gave me a fit. 他考试及格了，使我大吃一惊。
When she told her father that news, her father had a fit. 当她告诉她父亲那个消息时，她父亲大发脾气。