Hi! Saskia for BBC Learning English here,
and today I'm going to tell you about
how we use verbs of perception in English.
There are a number of these verbs
but I'm just going to look at two with you now:
see and hear.
When we use these verbs, this is the form:
First, the verb of perception.
Then, the object of the sentence.
Then we have either
the infinitive without to or the -ing form.
Here's an example:
I heard him go down the stairs.
Or:
I heard him going down the stairs.
There's a slight difference between these two forms:
When we use the infinitive,
it suggests that we hear or see
the whole action or event.
Using the –ing form suggests that
we hear or see something in progress.
'I saw her cross the street'
means I saw her cross from one side to the other.
'I saw her crossing the street'
means I saw her in the middle – on the way across.