6 Describing function

We use used to, (used) for, used as to describe the function of an object in positive and negative sentences, and in questions.

used to + infinitive

A torch is used to provide light.

Tasers aren't used to protect computers.

Is a baton used to monitor criminals?

(used) for + -ing form

This expression has the same meaning as be used to + infinitive.

Handcuffs are (used) for restraining someone. The baton isn't (used) for monitoring criminals. Is a PIN (used) for protecting cards?

Note that although we can leave out used in be used for, we cannot leave out used in the expression be used to.

Note: Don't confuse these expressions with be used to + -ing form, which means 'be accustomed to'.

used as + noun

This expression also describes the purpose of an object, to show that it is similar to the function of another object.

The belt is used as a weapon.

The handcuffs aren't used as a weapon.

Is the torch used as a signal?

We cannot use this expression if the two objects have exactly the same function.

not Л torch is used as a light.

7 Present Passive

One way to describe processes is to use the Present Simple.

The plastic travels through the barrel. The mould is now cool.

However, it is more common to use the Passive. This is because, when talking about a process, it is often not important or relevant to mention who performs an action.

Some verbs, such as verbs which do not take an object, e.g. travel, or verbs of thinking and feeling, e.g. be, cannot usually be used in the Passive.

not The plastic is travelled through the barrel.

Present Passive

Positive

The dough is cut into loaves.

The loaves are left to cool.

= subject + am /is/'are + past participle Negative

The plastic isn't melted by the hydraulic fluid. The screws aren't pushed back by the ram.

= subject + am/is/ are not + past participle Questions Short answers

Is the hopper filled with plastic? Yes, it is.

No, it isn't. Are the loaves sent to the shops? Yes, they are.

No, they aren't.

= Am / Is / Are + subject + past participle How is the plastic melted?

= Question word + am / is /are + subject + past participle

Although in general contexts the Passive can have I/ you / we as the subject, when talking about processes the subject is generally the pronoun it or they, or a singular or plural noun.

Note: The Passive can be followed with by if we need to clarify who or what has caused the action.

Grammar reference 119

8 Prediction: will, may, might

will

We use will to talk about future developments that we are certain about.

Positive

One sensor will stop the driver falling

asleep.

= subject + will + infinitive Negative

Traffic congestion will not be an easy problem to

solve.

= subject + will not (won't) + infinitive Questions

How will the car of the future be powered? Will the car of the future be very different?

= (question word +) will + subject + infinitive

may and might

We use may and might when we are less certain about future developments, i.e. when we think that something is possible rather than definite. May is more formal than might, but there is little difference in the level of possibility they contain.

Positive

A hybrid car may / might be the best choice.

= subject + may / might + infinitive

Negative

A noise-free bike may not / might not be popular

with bikers.

= subject + may / might + not + infinitive Questions Might hydrogen fuel cells get cheaper?

= Might + subject + infinitive How might the car of the future be powered?

= question word + might + subject + infinitive

We can use the short form mightn't in spoken English,

but there is no short form for may not.

Traffic congestion mightn't be an easy problem to solve.

not Traffic congestion mayn't be an easy problem to solve.

May is not used when we are asking people for their opinions, in order to avoid confusion with may in requests.