等久i
不是什么时候用的问题，而是怎么理解和运用动词不定式的问题，
这需要平时对一些词和短语的固定用法有很好的记忆和理解及运用，比如，try to do sth. ask sb. to do sth . want to do sth. expect to do sth ,等等，情态动词后一般都省略to，比如 will do , can do ,must do, shall do ,总之学习需要日积月累，一点一滴，坚持不懈，分分秒秒
阿三思234
1） 动名词与不定式的区别：
动名词表达的是：状态,性质,心境,抽象,经常性,已发生的
不定式表达的是：目的,结果,原因,具体,一次性,将发生的
2） 接不定式或动名词,意义相同.
3)在下列情况下,一般要用不定式：
①hate,like,love前有would(should)时,如：I'd like to have a cup of coffee.
②当谓语动词begin,continue,start等是进行式时,如：Thestudents are starting to work on the di fficult maths problem.
③begin,continue,start与know,understand等状态动词连用时,如：I soon began to understand what was happening.
⒋advise,allow,encourage,forbid,permit等动词后接动名词作宾语,或带不定式作宾语补足语.如：
Our teachers don't permit our swimming in the lake.
Our teachers don't permit us to swim in the lake.
4） 部分动词后接不定式或动名词时,意义差别较大,应根据句子语境选择使用.
①forget,remember,regret后接不定式,表示现在或未来的动作,接动名词表示动作已经发生.如：
Don't forget fo post the letter for me.
Have you forgotten meeting her in Beijing Airport?
Remember to close the windows before you leave.
I remember writing him a letter a year ago.
We regret to tell you that all of you are not invited toattend the meeting.
They regretted ordering these books from abroad.
动名词与不定式语义不同的有11 组：
1 stop to do stop doing
2 forget to do forget doing
3 remember to do remember doing
4 regret to do regret doing
5 cease to do cease doing
6 try to do try doing
7 go on to do go on doing
8 afraid to do afraid doing
9 interested to do interested doing
10 mean to do mean doing
11 begin/ start to do begin/ start doing
LUCY中小学英语课堂
好的。总体来说，不定式，英文中是infinity，不确定性，也就是表示没有做，英文中很多动词后面用不定式，比如would like/want/need/plan/decide/determine...都是表示打算做，计划做，决定做，可事实上还没做。不定式还有种主流用法在表目的，比如To succeed in the upcoming job interview,I have to familiarise myself with those skills required by the position.至于动词ing用法也非常广泛，一种是表示进行时，这个不多解释，还有是介词后面很多时候也加ing。这里稍微难点的就是ing做非谓语动词可以做主语，Speaking a foreign language seems to be a challenge to me.还有ing表示后置定语，表主动 Do you take notice of the man holding a cigarette?(The man holds a cigarette).最后讲一个ing表示结果，Setting fireworks is banned during spring festival,leading to a public demonstration.leading to表示结果。当然某些词后面既可以加ing也可以加to,do。Let's stop working.(别干活了，该吃睡了。)Let's stop to work.(别玩啦，该干活了) I remember borrowing you some money,now let me pay back. I remember to hand in my assignment,otherwise I'll be asked to write lines(罚抄).
最后建议，多阅读多听，语法必须结合语境。
中高考英语命题研究
1） 动名词与不定式的区别：
动名词表达的是：状态,性质,心境,抽象,经常性,已发生的 不定式表达的是：目的,结果,原因,具体,一次性,将发生的
2） 接不定式或动名词,意义相同.
3)在下列情况下,一般要用不定式：
①hate,like,love前有would(should)时,如：I'd like to have a cup of coffee.
②当谓语动词begin,continue,start等是进行式时,如：Thestudents are starting to work on the di fficult maths problem.
③begin,continue,start与know,understand等状态动词连用时,如：I soon began to understand what was happening.
⒋advise,allow,encourage,forbid,permit等动词后接动名词作宾语,或带不定式作宾语补足语.如：
Our teachers don't permit our swimming in the lake.
Our teachers don't permit us to swim in the lake.
4） 部分动词后接不定式或动名词时,意义差别较大,应根据句子语境选择使用.
①forget,remember,regret后接不定式,表示现在或未来的动作,接动名词表示动作已经发生.如：
Don't forget fo post the letter for me.
Have you forgotten meeting her in Beijing Airport?
Remember to close the windows before you leave.
I remember writing him a letter a year ago.
We regret to tell you that all of you are not invited toattend the meeting.
They regretted ordering these books from abroad.
动名词与不定式语义不同的有11 组：
1 stop to do stop doing
2 forget to do forget doing
3 remember to do remember doing
4 regret to do regret doing
5 cease to do cease doing
6 try to do try doing
7 go on to do go on doing
8 afraid to do afraid doing
9 interested to do interested doing
10 mean to do mean doing
11 begin/ start to do begin/ start doing
非谓语动词的用法是英语语法的一大难点,你最好全面对比一下不定式、动名词、现在分词、过去分词以及独立主格结构的用法!
亚历山大罗夫
英语，何时用不定时，何时用动名词？
1. 1) 某些特定动词，一般只接不定时，如，want，plan，promise，decide，agree等等。
Tom decided to plan to agree to join us
2)某些动词后，一般只接动名词，如，enjoy，finish，avoid，quit，keep等等。
He enjoys keeping finishing doing his homework first.
另外，介词后接动词，用动名词形式。
By working hard,he succeeded in passing the final exam.
2. 有些动词后，即可接不定式，也可接动名词，但，表达的含义不同。如，
1) forget to do，忘记去做(未做)
forget doing，忘记做过(已做)
2) remember to do，记得去做(未做)
remember doing，记得做过(已做)
3) regret to do，后悔/遗憾去做(未做)
regret doing，后悔做过(已做)
4) need to do，
need doing=need to be done
5) like to do，(多接，一次性偶然性的动作)
like doing，(多接，经常性习惯性的动作)
Tim likes running outside，but today he likes to stay at home.
3.动词不定时，多表，目的，结果，将来。。
动名词，表主动。
To finish the project on time(表目的)，the experts are busy investigating.
4.动名词和动词不定式，都可以做主语或宾语。此时，一般，动名词表抽象动作，动词不定式表具体动作。另外，不定式做主语或是宾语时，通常用it做形式主语或是形式宾语，而真正的主语或宾语放到后面。
It has taken us almost half a month to fight against the coronavirus(新型冠状病毒).
GorillaEnglish
同学你好~
1.表示一般的、泛指的或习惯性的行为用动名词；表示具体的、一次性的或将来的动作用不定式。如：
Swimming is fun in summer. 夏天游泳是有趣的事。
Swimming in this river is a great pleasure. 在这条河里游泳是件非常快乐的事。
注：有时这种区别并不很严格。但要注意：主语和表语要用同一种形式；平行结构中要用同一种形式。如：
To see is to believe. = Seeing is believing. 眼见为实。
Fishing is his favorite hobby, and collecting coins also gives him great pleasure 钓鱼是他的爱好，集邮也给他带来极大的乐趣。
2.口语中，陈述句多用不定式作主语，而疑问句却总是用动名词作主语。如：
Is doing morning exercises good for your health? 做早操对你身体有好处吗？
3.下列句子中通常要用动名词：
It’s no good/use talking to him. 找他谈是没有用的。
It’s useless discussing the matter. 讨论此事无益。
There is no stopping him. 无法阻止他。
No parking! 禁止停车！
4.下列句中通常要用不定式：
It took us two hours to get there. 去那里我们花了两个小时。
It’s foolish of him to do so. 他这样做是愚蠢的。
It is necessary for us to learn English well. 我们有必要学好英语。
▲还有一点要补充一下：
动名词作主语并不是表示某动作正在进行，而是表示经常性或习惯性的行为；不定式的进行时作主语才表示具体的某一动作正在进行。比较：
It's nice having friends to chat to. 有朋友聊聊天是很惬意的。（经常性、一般性或习惯性的行为）
It's nice to be talking with you here. 在这里跟你交谈是非常愉快的。（一次具体的正在进行的行为）
谦谦语文
你说的是，哪些动词和短语后面接不定式或动名词吧？
常见的动词和短语后面接不定式，如decide, refuse, want , wish, expect 等。
常接动名词的有，enjoy, finish, feel like, avoid, imagine, appreciate , can't help(情不自禁), fancy 等。大体上，想要愿望类一般用不定式，喜欢想象类一般接动名词。
英语老师Jerry吴
不定式：to do something，表达的主要是将要做什么，如果有打算表达一种意愿或计划、打算，此时即可使用不定式，如would like to do something, want to do something。
动名词:doing something，主要表达的是现在正在做什么，如我正在喝水，I am drinking water. 当然，如果很近的将来也可以用动名词表达，如我正要去学校，可以用 I'm going to school.
在使用中，建议结合谈话的语境和上下文来进行选用。
