动词不定式进行式表示动作正在进行，与谓语动词表示的动作同时发生。如：

He see ms to be recovering.他看来在康复。

When he came in，I happened to be lying on the bed，reading. 他进来的时候，我碰巧正躺在床上看书。

[英语语法手册]非限定动词 E

动词不定式的被动语态

动词不定式有两种被动语态形式：

一般式to be written

完成式to have been written

例：

The next thing to be done is to carry away the earth.下-步要做的事是把土运走。

No harm seems to have been done.似乎并没有造成损害。

分裂不定式

有时在不定式符号to和动词原形之间插入一个副词，这种现象叫做分裂不定式(split infinitive)。插入动词不定式的副词，习惯上往往与不定式动词连在一起。如：

He likes to half close his eyes.他喜欢半闭着眼睛。

Our object is to further cement friendly relations between the two countries.我们的目的是进一步加强两国之间的友好关系。

At first he wasn't interested in bookkeeping，but later he began to actually like it.起初他对会计工作没有兴趣，但到后来倒喜欢起它来了