to什么时候后接动词原形,什么时候接ing形式?He always has a lot of new things to learn.这里的to learn为什么要加to?Do you like to work late?这里为什么要加to?Do you want to work with actors?这里为什么要加to?actors 为什么要加s?

加s是复数形式，而当to是与动词构成不定式时是跟原形，而to做介词时是跟ing

1.things to learn, to do 不定式做定语，修饰things，要学习的东西;
2.like to work late, 这里的to work late 做like的宾语，喜欢工作很晚，其实这个也是固定搭配，like to do something 喜欢做某事；
3.want to work with actors, 这里的to work with actors 也是做want 的宾语，同样是固定搭配，want to do something 想要做某事；
4.actor用复数actors, 说的是泛指所有的演员，不具体到某一个人。

to 用作动词不定式时接动词原形,表示某个动作；用作介词时接动词ing或是名词1.things to learn,修饰things,to do 作定语,句意表示要学习的东西;2.like to work late,这里是like的固定搭配,like to do或是like doing ...

to do中的to 是不定式符号。后接动词原形。而to doing中的to是介词后接动词名词。如
I would like to work here.
I have been used to working here.
We must devote all our energy to studying .
actors是复数名词表示一类。再如 We are students.