see / hear + object + verb form

Both see and hear, and also notice and watch and other verbs of perception, can be followed by object + bare infinitive (i.e. without to) or by object + verb-ing.

•     At about one o' clock in the morning I heard my daughter unlock the door and come in.
•     At about one in the morning I heard my daughter unlocking the door and coming in.
•     I watched my brother scrape the ice off the car windscreen.
•     I watched my brother scraping the ice off the car windscreen.

There is often, however, a slight difference in meaning. If we use the verb-ing form, there is a suggestion that we are witnessing the event in progress, whereas if we use the bare infinitive, this suggests that we can hear or see the complete action or event.

Compare the following:

•     As I passed their classroom, I could hear them whispering inside.
•     At the party, I heard Sue whisper to Tom: "Let's get our of here before Barry arrives."
•     I watched Henman play Hewitt in the men's singles semi-final at Wimbledon
•     I saw them playing in the garden, but I didn't take much notice.

We can use see and hear in the passive voice, but if we use it with an infinitive then to is required. The verb-ing form is not affected.

Compare the following:

•     She was heard to mutter "I shall never forgive you" as she went out of the room.
•     Everybody heard her mutter "I shall never forgive you" as she left the room.
•     He was seen climbing out of the window.
•     They all saw him climbing out of the window.

                
          make +object + infinitive

Make is followed by object + bare infinitive. It cannot be followed by object + verb-ing

•     I made him wait. I had no intention of speaking to him while he was in such a foul mood.
•     She didn't want to do it, but he made her do it.

We can also use make with a reflexive object, myself, yourself, himself, herself, etc and a past participle, particularly with the verbs understood and heard:

•     She doesn't speak English very well but she can make herself understood in most situations.
•     There was so much noise at the party that I had to shout all the time to make myself heard.

We can also use make in the passive voice, but in this case to before the infinitive is needed:

•     He had done so badly that he was made to repeat the school year.
•     He had borrowed over five hundred pounds and was made to pay it back in monthly installments.

                
            let + object + infinitive

Like make, see and hear, let is followed by object + bare infinitive. It cannot be followed by verb-ing:

•     Let me carry that box of papers for you. It's very heavy.
•     Why don't you let him walk home by himself from school now? He's eleven years old after all

Let is also frequently used in the expression let's (let us) to introduce a suggestion. Note that negative sentences with let's can be formed in two possible ways:

•     Let's finish the video tomorrow, shall we? I'm tired and I want to go to bed.
•     Let's not be late home tonight. It's Monday tomorrow after all.
•     Don't let's get too stressed about this. I know the car is damaged, but it's only a piece of metal.

We do not normally use let in the passive voice.
    
                
            allow / permit + object + infinitive

Allow and permit are the more formal equivalents of let. But they both require to before the infinitive. Permit sounds a bit more formal than allow. Compare the following:

•     Let me bake the cakes for the party.
•     Allow me / permit me to bake the cakes for the party.
•     I would never let him smoke in the bedroom.
•     I would never allow him / permit him to smoke in the bedroom.

Allow and permit are often used in the passive voice. Remember, we cannot use let in these examples:

•     I wasn't allowed to pay for my meal. Tony insisted on inviting me.
•     Young children should not be allowed / permitted to watch television after nine o' clock.