Чтобы не повторяться,
– можно от инфинитифа оставить только ‘to’
He had to go to work, but she didn’t want to.

– можно использовать ‘to’ только перед первым инфинитивом
To give is better than (to) receive.
It’s better to do everything now than (to) leave it to the last minute.
I’m going to go out and have a good time.

SPLIT-INFINITIVE – когда между ‘to’ и глаголом вставляется наречие (слово, отвечающее на вопрос ‘как?’)
I didn’t expect you to suddenly change your mind.
No one claims to really understand what is happening.
They are planning to secretly test a new and more powerful weapon.

Предлоги, как правило, остаются на своих обычных местах
Your meals are all you have to pay for (‘…all for which you have to pay’ звучит формально)
There’s nothing to get excited about (лучше, чем ‘… about which to get excited’)
I need a vase to put these flowers in (лучше, чем ‘… in which to put these flowers’)

Инфинитив в роли подлежащего
To defrost this fridge takes ages.
To turn down the invitation seems rude.
Not to take a holiday now and then is a great mistake.
Но чаще используется ‘it’ в роли ‘пустого’ подлежащего
It takes ages to defrost this fridge.
Would it seem rude to turn down the invitation?
It‘s a great mistake not to take a holiday now and then.

Инфинитив для выражения
– цели
Cover the turkey in silver foil to keep the meat moist.
Laura has gone to town to do some shopping.
We bought a cage for John to keep the hamster in.
I’m writing to inquire about activity holidays.
To get a good seat, you need to arrive early.
В более формальном варианте – ‘in order to’ ИЛИ ‘so as’
Interest rates have been raised in order to reduce inflationary pressure.
We have removed the warning signs so as not to alarm the public.
– результата
Laura came home to find her house on fire.
He grew up to be a handsome young man.
– плохой новости (с ‘only’)
I found my keys only to lose them again.
Charles arrived for the concert (only) to find it had been cancelled.

Seem, appear
Sarah seemed to be quite annoyed.
The computer program appears to have a bug in it.
The person I spoke to didn’t seem to know anything about the company’s products.
Continuous: Andrew seems to be studying even harder these days.
Perfect: David appeared to have hurt himself.

Tend, manage, fail
We tend to get up later at weekends (= We usually get up later at weekends.)
Luckily I managed to find my way here all right (= I was able to find my way.)
David failed to pay his electricity bill.

Certain, sure, (un)likely
United are certain / sure to win (= They will certainly win)
Sarah is likely to be at work (= She is probably at work)
The peace talks are likely to last several weeks.
The party is sure to be a great success.

For, of
It’s important for drivers to take care.
It isn’t safe for children to play on ladders.
Если речь идёт о чьём-то поведении, используется ‘of’
It was polite of Emma to write and thank us (= Emma was polite)
It was silly of me to forget the tickets (= I was silly)

СХЕМЫ ИСПОЛЬЗОВАНИЯ ИНФИНИТИВА
It was marvelous to visit the Grand Canyon.
It is difficult to solve the problem.
It is rare to see a horse and cart nowadays.
It felt very strange to be watched by so many people.
It is rather unexpected to meet you here.

The Grand Canyon was marvelous to visit.
Your writing is difficult to read.
A small car would be cheap to run.
The parade was fascinating to watch.
The ladder is quite safe to use.
The problem is difficult to solve.
Would gas be any cheaper to cook with?

There’s the question of who to invite to the reception.
You need to be informed about what to do in an emergency.

It’s too difficult to work the figures out in your head.
The coffee was too hot to drink.
This rucksack isn’t big enough to get everything in.
There’s too much work for you to finish today.
The kitchen is too small for the whole family to eat in.
The light wasn’t shining brightly enough for anyone to notice it.

We were sorry to hear your bad news.
You were clever to find that out.
You were lucky to win the game.

I’ve got some letters to write.
The doctor had a number of patients to see.

We’ll have to decide whether to go ahead with the project (or not) (NOT … if to go ahead…)
Melanie wasn’t sure whether to ring the doctor or not (NOT … if to ring…)
I was wondering whether to order some tea (NOT … if to order…)
We’ll have to decide whether to go (or not) (NOT … if to go…)

I’ll wait for you to finish your breakfast.
We’ve arranged for a photographer to take some photos.
There are telephones for drivers to call for help if they break down.
For plants to grow properly, you have to water them regularly.

BARE INFINITIVE
1. после модальных глаголов
Nothing can go wrong.
They must be having a party next door.
You should be more careful.
You could have made the tea.
НО
‘to-infinitive’ после ‘ought to’, ‘have to’, ‘be able to’, ‘be allowed to’, ‘be going to’
You ought to be more careful.
You have to put some money in.
I was able to get home OK.
We aren’t allowed to walk on the grass.

2. после ‘had better’, ‘would rather’ / ‘would sooner’, ‘rather than’
We’d better not be late.
I didn’t enjoy it. I’d rather have stayed at home.
They decided to accept the offer rather than go to court.

3. после ‘see’, ‘(over)hear’, ‘feel’, ‘observe’, ‘notice’, ‘watch’
They saw the lights come on.
We all heard the bomb go off.
She noticed him run away from the house,
Someone saw the men leave the building.
I thought I heard someone knock on the door.
+
‘have’, ‘let’, ‘make’
I made Peter wait outside.
Let me help you.

4. после ‘except’ и ‘but’
As for the housework, I do everything except cook.
You’ve done nothing but grumble all day.

5. в этой схеме после ‘to be’ – ‘bare infinitive’ ИЛИ ‘to-infinitive’
The only thing I can do IS (to) apologize.
What the police did WAS (to) charge into the crowd.
What I want to do IS (to) make a fresh start.

6. после ‘help’ можно ‘bare infinitive’ ИЛИ ‘to-infinitive’
Vicky helped me (to) choose a present.
I’ll help you (to) arrange the party if you like.

‘Вare infinitive’ НЕ ИСПОЛЬЗУЕТСЯ в Passive!!
The men were seen to leave the building at half past six.
She was made to cut her hair.
The car was heard to drive away.