Too 只有一个词性，那就是副词，它可以作为程度副词，修饰其他的形容词或副词。虽然它的词性只有一个，但是它的用法不止一个，特别是当它与其他单词连用时，衍生了不少让人困扰的语法。
一、修饰形容词或副词
Too 修饰形容词或副词时，直接置于所修饰词的前面，意为“太，过于，过度”，例如：
The dress was too tight for me.
这件连衣裙对我来说太紧了。
This coffee is too sweet.
这咖啡太甜了。
It happened too quickly, so I didn’t see it.
事情发生得太快了，所以我没看到。
The car was travelling too fast and went out of control.
汽车开得太快，失控了。
二、肯定句中的“too 形容词/副词 to（带 to 不定式） ”结构
1. 若动词不定式与前面的 too 呼应， 则该结构有否定意义，意为“太…而不能…”，此时的动词不定式在句中作结果状语，例如：
He earns too little to keep his family in comfort.
他挣的钱太少而不能让家人过得舒适。
I know him too well to like him.
我太了解他了而不能喜欢他。
The water was too cold to swim in.
水太冷了，游不进去。
She is too clumsy to handle glassware carefully.
她笨手笨脚，拿不动玻璃器皿。
2. 若动词不定式不与前面的 too 呼应，而是修饰表“积极”意义的形容词，则该结构没有否定意义，此时 too 通常含有 very 之意，且前面常有类似于 only，but 或 all 等副词修饰，意为“很，非常”，例如：
I was only too glad to help him if he asked.
如果他提出来，我非常乐意帮助他。
解析：此句相当于 I was very glad to help him if he asked.
He is too ready to make promises.
他非常急于许下诺言。
解析：此句相当于 He is very ready to make promises.
It was all too easy to believe it.
这很容易令人相信。
解析：此句相当于 It was very easy to believe it.
三、too 与否定词
Too 与否定词连用，表示缓和语气、礼貌或谨慎，意为“太，十分”等，此时的 too 有 very 的味道，例如：
a. We're not too worried by these results.
我们对这些结果并不太担心。
b. start work on it now so we're not too rushed at the end.
我们现在就开始干吧，免得最后太匆忙。
c. It's not too late to learn.
✔：现在学习还不晚。
d. It's never too late to improve your diet.
✔：什么时候改善饮食都为时不晚。
注意：句 c 和 d 中的“too … to ”结构已经没有否定意义了，所以以下翻译是错误的：
四、too 与 much，many，few，little
当要谈论数量多少的时候，在名词之前使用 too much，too little，too many，too few，其中前面两个修饰不可数名词，后面两个修饰可数名词，例如：
There's too much salt in this soup.
这汤里的盐太多了。
The trip was cancelled because there was too little interest in it.
旅行取消了，因为大家对它兴趣太少。
There were too many dogs on the beach.
海滩上的狗太多了。
I don’t like this book because there are too few pictures in it.
我不喜欢这本书，因为里面的图片太少了。
五、too 与 far，much
Far 或 much 与 too 连用表示强调，其中 far too 所表示的程度比 much too 大，例如：
另一个太贵了。
much too: The other one was much too expensive.
far too: The other one was far too expensive.
你对我实在太好了。
much too: You are much too kind to me.
far too: You are far too kind to me.
注意：too much 与 much too 是完全不一样的，它们对应的中心词分别是 much 和 too，那么区别也基本上就是 much 与 too 的区别了。
六、too 与 very
1. 虽然 too 有时有 very 的味道，但是当要强调形容词或副词时，只用 very，而不用 too，这个可以从中文意思中区分开来，too 和 very 所表达的味道截然不同，例如：
