The quotation from Cambridge Advanced Dictionary

When the sun goes down, it moves down in the sky until it cannot be seen any more

On summer evenings we would sit on the verandah and watch the sun go down.

"The sun goes down" looks right due to "the sun" we can substitute to "it". And verb for "he, she, it" should be with "s/es". But why in 2nd sentence we use the verb - "go", not "goes"?


2 Answers 2


In the second sentence, "go" is in the infinitive (the form without "to") following the verb "watch" (I don't know what the proper term for that is). Infinitives are not conjugated to match a subject, so it's "go" and not "goes". Various verbs can take an infinitive like that, some with "to" and some without:

I helped Joe study for the exam.

Bill wants Jane to be on his team.

  • You got that completely wrong. An infinitive is a verb with "to". "to" is what puts a verb into its infinitive form. The term "infinitive" basically means not bound by time. There's no time reference to speak of when we say "to err is human", for example. You can't tie it to a particular point on the time line. What we have there is called the bare form of a noun. For example, "to see" is the infinitive form of the verb "see". "see" is its bare form. Commented Apr 19, 2016 at 23:29
  • 1
    What you call the "bare form" is still an infinitive, just a bare infinitive. See en.wikipedia.org/wiki/Infinitive. Commented Apr 20, 2016 at 0:17

Long story short, we don't use the to particle with verbs that describe actions having to do with the faculties of vision, hearing and so on. The most common ones include verbs like to hear, to feel, to watch, to see etc. These are the only ones that I can think of at the moment. There are probably a couple more, but to tell you the truth, the list is fairly short. There are really not that many of them in English.


I've never heard people say that in American English.

I saw it fly over my house before it crashed in the forest.

One thing I like most of all is kick back and watch other people do my work for me.

The other ones that are not part of the "sense verbs" group are to make, to let and to help. to help is somewhat controversial. In modern American English, people don't usually use to with to help, though, very rarely, you will see it used sometimes.


— Why did you kill your mother?
— It wasn't really me who killed her. The voices in my head made me do it.

Don't let the kids play with that dog. It might have rabies or other kind of dangerous disease.

Can you help me do my homework tonight?

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