字不能无。动词let属例外，其宾补/主补“to”均无。
扩展资料
I never have the time to go out in the week.
我从星期一到星期五从来没有时间外出参加社交活动。
Now she won't have to go out to work any more.
现在她不必再出去工作了。
一感：feel
二听：hear，listen to
三让：make，let，have
四看：see，notice，watch，observe
半帮助：help.
【注意】在下列结构后常用不带to的动词不定式：had better， would rather， do nothing but， why not等。
例如：
I’d better go now， or I’ll miss the train.
动词不定式的一般形式是“to＋动词原形”，但在下面情况中to要省略：
一、在感官动词see， hear， watch， notice， feel， look at， listen to等及使役动词make， let， have等后作宾语补足语的动词不定式要省略to。如：
We saw him get on a bus.
The boss often made the workers work for over 12 hours a day.
注意：以上情况如果用于被动语态时，不定式符号to一定要补回。如：
He was seen to get on a bus.
The workers were often made to work over 12 hours a day.
二、在动词help后作宾语补足语的动词不定式符号to可带可不带。如：
I often help my mother (to) do housework.
三、在had better， would rather后动词不定式不能带to。如：
You’d better not go out at night.
The boy would rather stay at home by himself.
四、当两个或两个以上的动词不定式并列使用时，通常只有第一个不定式前带to，第二个及以后的不定式可省略to。如：
I want to have a read and write.
He wants to have a rest and have a cup of tea.
五、“Will(Would) you please＋不带to的不定式”。如：
Would you please not do that again?
六、当不定式作介词but， except的宾语，表示“除了……不/没有做……”时，不定式要省略to。如：
She does nothing but watch TV.
She doesn’t want to do anything except sleep
