反射不定式是指不定式与句子的主语构成动宾关系,此时的不定式主动形式表示被动意义，例:1．n. + be + adj. + to do.

(反射不定式，不定式与句子主语是逻辑上的动宾关系）

e.g. The man is hard to deal with.

The water is not fit to drink

2．n.+ be + too + adj.+ to do.

(反射不定式，不定式与句子主语是逻辑上的动宾关系）

e.g. The box is too heavy to carry.

Many stars are too small to see.

3．n. + be + enough + to do.

(反射不定式，不定式与句子主语是逻辑上的动宾关系）

e.g. The bag is light enough to carry.

This kind of work is easy enough to do.

此称之为反射不定式。