动词不定式

　　不定式定义：由to+动词原形构成。不定式是一种非限定性动词。而非限定动词是指那些在句中不能单独充当谓语的动词，可分为不定式，动名词，现在分词和过去分词。“动词不定式”由动词+不定式构成。动词不定式在句中可以作句子除谓语之外的任何句子成分。动词不定式的被动形式除了一般形式外还有其完成式和进行式。

　　动词不定式 语态

　　如果动词不定式的逻辑主语是这个不定式所表示的动作的承受者，不定式一般要用被动语态形式。如：

　　It's a great honour to be invited to Mary's birthday party.(不定式作主语是被动语态to be invited是被邀请)

　　It was impossible for lost time to be made up.(不定式作主语)

　　I wish to be sent to work in the country.(不定式作宾语)

　　Can you tell me which is the car to be repaired?(不定式作定语)

　　He went to the hospital to be examined.(不定式作状语)

　　在There be结构中，修饰主语的不定式可用被动，也可用主动。如：There are still many things to take care of (to be taken care of).但有时两种形式表达的意思不同，如：There is nothing to do now.( We have nothing to do now.) There is nothing to be done now.(We can do nothing now.)

　　动词不定式　时态

　　1) 现在时：一般现在时表示的动词，有时与谓语动词表示的动作同时发生，有时发生在谓语动词的动作之后。

　　He seems to know this.

　　I hope to see you again. = I hope that I'll see you again.　我希望再见到你。

　　2) 完成时：表示的动作发生在谓语动词表示的动作之前。

　　I'm sorry to have given you so much trouble.

　　He seems to have caught a cold.

　　3)进行时：表示动作正在进行，与谓语动词表示的动作同时发生。

　　He seems to be eating something.

　　4)完成进行时：

　　She is known to have been wreaking on the problem for many years.

　　一般在表示情绪的动词后加to do也表将来