The infinitive without "to"

This is a small group of verbs. The infinitive without "to" is used:

1. after modal verbs (except ought to)
   
   
2. after "let" + object
   
   
3. after "make" + object
   N.B. The to-infinitive is used after make in the passive (I was made to laugh.)
   
   
4. after the following expressions:
   
   had better
   would rather (not)
   would sooner (not)
   
   
5. after verbs of perception if we perceive the entire action (from start to finish)
   
   see, hear, feel, watch
   N.B. If we observe only a part of the action, we use the -ing form!! - I saw him crossing the street (=He was already in the middle of the street when I saw him)

The infinitive with "to"

Most English verbs are followed by the infinitive with to. Some can be with or without an object depending on meaning.

1. Here are only a few examples of verbs that use this pattern:
   
   agree, appear, afford, choose, decide,expect, fail, hesitate, hope, intend, learn, manage, mean, offer, plan, prepare, pretend, promise, refuse, tend, want, wish ......
   
   
2. Some verbs are followed by an object and the to-infinitive:
   
   allow, ask, encourage, expect, invite, order, persuade, remind, teach, tell, want
   N.B. We do never use want with a "that"-clause. We cannot say "I want that you come."

The Gerund(-ing)

1. Some verbs MUST be followed by the gerund:
   admit, anticipate, appreciate, avoid, can't help, can't resist, complete, consider, delay, deny, discuss, dislike, enjoy, escape, fancy , finish, imagine, include, involve, justify, keep, mention, mind, miss, postpone, practise, quit, reject, resist, risk, suggest, tolerate, understand.
   N.B. allow - advise - forbid - permit are followed by the gerund in general statements (They don't allow smoking in the library.)
   If the person is mentioned, the infinitive must be used!! (They don't allow people to smoke in the library.)
   
   
2. a preposition MUST always be followed by the gerund:
   (adjective) + (prepositon) + (-ing)
   He is good at swimming. She was proud of having won the match.
   (noun) + (preposition) + (-ing)
   John has no excuse for being late. He had no hope of getting a job.
   (verb) + (preposition) + (-ing)
   We are looking forward to seeing you. I apologise for coming late.
   
   
3. after certain expressions:
   to be busy, to be like, to be near to, to be no good, to be no use, to be worth

Infinitive or Gerund with NO difference in meaning

The following verbs can be followed by either an infinitive or a gerund with no difference in meaning:

1. begin, can't bear, can't stand, continue, hate, like, love, prefer, start
   It began to rain. / It began raining
   N.B. would + hate/like/love is usually followed by the infinitive (I'd like to go now)

Infinitive or Gerund WITH a difference in meaning

We can use some verbs with both the to-infinitive and the gerund but with a change of meaning. The most common of these are:
forget, go on, regret, remember, stop, try

1. She'll never forget making her first phone call abroad.
   She forgot to post the letter to John.
   
   forget doING something
   forget to do something

The same rule applies to the other words

Verbs of perception

As mentioned above, verbs of perception (feel - see - watch - hear - notice) can be followed by the to-infinitive or the gerund with a difference in meaning.

1. The -ing form is used when we are talking about observing part of a completed action - in other words, when we start looking, listening, etc., the action is already going on and/or will not be completed.
   When I looked out of the window, I saw Henry crossing the road. (Henry was already in the middle of the road when I looked.)
   I saw the man crossing the river. (=I saw how he was fighting against the current.)
   
   
2. The infinitive is used if we observe the whole action from start to finish
   I watched the man open a can of beer, pour it into a glass, and drink it in one go.
   I saw the man cross the river (I saw him leave the one bank and reach the other.)