为什么省略了to？

Question

It is also the reason why when we try to describe music with words, all we can do is articulate our reactions to it, and not grasp music itself.
is和articulate中间省略了to,为什么能省略?

Answer 1

一、使役动词（have、let、make）后省略，
至于为什么，我觉得应该是如果带to就显示不出命令、要求等这些奖励的语气了，就如同No smoking,如果要说成Not smoking,就少了那份肯定，
省略类型如：
My mother wouldn’t let me （to）go to the film.
I don’t like milk, but mother made me （to）drink it.
I would have him （to）wait for me at the gate of the park.

二、感觉动词[feel、hear、see、notice、listen(to)、look at、smell、observe、watch(注视、观看)、overhear(偷听)、perceive(观察)]后省略，
至于为什么这个也要省略，应该是和“I mean”一样的习惯问题，这是一个口头禅，一般都连着来，后面的可以情况另取状态，这样就好理解了，
如：
I watched her （to）get into the car.
We often hear her （to）sing this song.
I saw the woman （to）enter a bank.
三、help后也常省略，
如：
Can I help (to) carry this heavy box?
四、know后也常省略，
当know已经是过去，或已经完成的时候，即knew,have known时，可省略，如：
I never knew him (to) do such a thing.
We've never known him (to) tell a lie.

注，当 know 为现在式,该结构中的不定式只限于 to be,且其中的to不能省略.如：
We knew her to be honest.
五、主语带do表语也可省略
如：
All you do now is (to) complete the form.

这里值得注意的是，只要这些能省略to的地方，变成被动后，就都不能省略了。

Answer 2

不定式作表语有时省略to，只留下动词原形。