Conditional sentencesWe use conditional sentences to describe how an action or situation affects its result.

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3 Types of Conditionals

Conditional sentences contain an if-clause and a main clause.

If I have enough money,conditional clause

Examples :

I will go to US.    main clause

I will go to U.S.    main clause

if I have enough money.    conditional clause

Conditional clause , main clause.

a. If you help me with the dishes (if + pres) , I will help you with your homework.

(will + inf)

b. If ice is heated, it melts. (Pres. tense).

c. If you see Mr. Tung tonight, tell him I am ill. (imperative).

1. If + Present Tense will +inf / present tense / imperative

We do not normally use will or would in the conditional clause, only in the main clause.

2. If + Past Tense 2. If + Past Tense

3. If + Past Perfect Tense3. If + Past Perfect Tense

would + infinitive would + infinitive

would have + past participle would have + past participle

e.g. If I knew her name, I would tell you.

e.g. If I had won the lottery, I would have bought a new house.

Uses of the conditional

First conditional

a. Nature: Open condition, what is said in the condition is possible.

b. Time: This condition refers either to present or to future time.

e.g. If the cinema is full, we will go to a restaurant.

e.g. If it rains tomorrow, we will stay at home and

watch TV.

Second conditional

a.Nature: unreal (impossible) or improbable situations.

b. Time: for present unreal events, we put the verb in the condition clause one step back — into the past:

e.g. If I were you, I would tell my father.

If I became president, I would change the medical care policy. (Said by a schoolboy: improbable)

Compare:If I become president, I will change the medical care policy. (Said by a presidential candidate)

Third conditional a. Nature: unreal

b. Time: for past unreal events — things that didn't happen, but we can imagine — we put the verb in the condition clause a further step back — into the past perfect

e.g. If I had studied hard for the exam, I would have passed

it easily. (But in fact, you did’t study hard.)

For the second conditional, were replaces was

If I were a rich man, I would stop working as a clerk.

If I were to lose my job, I wouldn't be able to pay for my dream car.

Instead of if not, we can use unless.

“ if ” + negative action = “unless” + positive action

The meaning of both sentences is the same, but the actionafter ‘unless’ (close) is the opposite of the action after ‘if’ (don’t close).

Compare:Your bird will fly away if you don’t close the window.

Your bird will fly away unless you close the window.