INFINITIVE OR GERUND?, GERUND OR INFINITIVE?

Sometimes we need to decide whether to use a verb in its: -ing form, gerund (doing, singing) or infinitive form (to do, to sing). For example, only one of the following sentences is correct. Which one?

We decided to take a taxi OR We decided taking a taxi

A) WHEN TO USE AN INFINITIVE:
1-always used AFTER ADJECTIVES, for example: disappointed, glad, happy, pleased, relieved, sad, surprised...

I was happy to help them. She will be delighted to see you.

- Including TOO+ADJECTIVE: The water was too cold to swim in.

Is your coffee too hot to drink?

- It is used after ADJECTIVE+ENOUGH: He was strong enough to lift it.

She is rich enough to buy two.

2- It's used to express PURPOSE*: He phoned to invite me to a party

*For+somebody+TO DO+something: This bench is for us to sit on /

*For+ing: A knife is used for cutting

3- It's always used after QUESTION WORDS+ a verb:

I don't know how to do it. He didn't say when to call him.

4- The infinitive form is used after certain verbs:- agree, allow, can/can't afford, choose, decide, encourage, expect, forget, help, hope, learn, manage, mean, offer, plan, pretend, promise, recommend, refuse, teach, train, want...

I forgot to close the window. We can't afford to take a long holiday.

5- With other verbs the structure is: VERB+(obj)+TO* infinitive: -allow, ask, expect,

help, invite, mean, order, recommend, remind, teach, tell, want, warn...The police ordered the people to leave.

He wanted me to go with him. I warned him not to come back late.

!!*- make & let: verb+obj.+infinitive without to. Let me do it.

6- Always with MODAL VERBS+infinitive without to: - can/could, may/might, must, need, shall/should, will/would. (Except: ought to).

She can swim very well. I'll see you tomorrow. You mustn't do that.

You should go to the doctor. / You ought to go to the doctor.

B) WHEN TO USE A GERUND (-ing):1- The -ing form is used as a noun and is the subject of a sentence or clause:

Swimming is good exercise. Doctors say that smoking is bad for you.

2- The -ing form is ALWAYS used after a PREPOSITION:
They left without saying "goodbye".

or a VERB+PREPOSITION*: - succeed in, insist on, think of...

He insisted on taking me home.

or EXPRESSIONS*: - it's no good/use, have difficulty, go+-ing...

It's no use in complaining He goes swimming every Tuesday.

!!* Watch out with:

- USED TO+infinitive: He used to wear glasses.

- BE/GET USED TO+ing: He's used to getting up early.

- LOOK FORWARD TO+ing: They are looking forward to visiting us this summer.

3- The -ing form is used after certain verbs: avoid, can/can't stand, carry on, dislike, enjoy, fancy, finish, give up, imagine, keep on, mind/not mind, miss, practise
I dislike getting up early. Would you mind opening the window?

C) Some verbs can be followed by the -ing form or the infinitive:
1) Without a big change in meaning: begin, continue, hate, intend, like*, love, prefer*, propose, start.
It started to rain. (common) - It started raining.
I like to play tennis. (it's good, right) - I like playing tennis. (I enjoy it).
!!*would like to+infinitive: I would like to live here.

!!*prefer +ing to +ing: I prefer driving to travelling by train.

prefer to infinitive rather than...: I prefer to drive rather than to travel by train.

would prefer to infinitive rather than...: I'd prefer to stay (rather than leave).

2) Others have a change of meaning depending on which is used:
- FORGET 
I forgot to tell him the news. (fail to do something)
I forget telling him the news but perhaps I did. do something and not remember)
-  REGRET 
I regret to inform you have to leave the country. (be sorry to+unpleasant info)
I regret settling in Britain. (a mistake in the past)
- REMEMBER 

I remember posting the letter. (= He remembers having done it. After)
Remember to post the letter when you go out. (Before doing it, remind you to do it.)
- NEED

I need to do more exercise. (It's necessary for me. You have to do it).
The batteries need changing. (Need as a modal verb. It needs to be done. Impersonal sentence).
- STOP

I stopped to talk to him. (It tells the reason for stopping).
He stopped walking. (It tells the action which stopped).
- TRY

I tried to keep my eyes open. (Effort, attempt).
Try pressing this button. (Experiment, test).

Summary verb chart:

Video GERUND / TO+infinitive:

Here are links to practice and test yourself on Gerunds & Infinitives:
On this blog.

English study quiz (1)
English study Quiz (2)

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