This document discusses the four types of conditional sentences in English: zero, first, second, and third conditional. It provides examples of each type and explains the tenses used in their clauses. Zero conditional sentences use the simple present tense in both clauses to talk about generally true situations. First conditional sentences use the simple present in the if-clause and future in the main clause to talk about possible future events. Second conditional sentences use past tense in the if-clause and modal verbs in the main clause to talk about hypothetical or unlikely situations. Third conditional sentences use past perfect in the if-clause and modal verbs plus perfect aspect in the main clause to talk about hypothetical past situations and their effects on the present.

1. INTRODUCTION
Conditional Sentences tell us that something
depends upon something else. In other words,
they tell us that an event can or will happen if a
particular condition is fulfilled. Conditional
sentences usually have two clauses: a main
clause and a dependent or subordinate clause
(an if-clause).
1. If my novel proves to be a bestseller, I
will be a millionaire.
2. I’m sure Sana will share her notes with
you if you request her.
In these sentences the main clause talks about
something that can happen and the dependent
clause tells us about the condition that must be
met for it to happen. There are four types of
conditional sentences: zero, first, second and
third.

2. ZERO
CONDITIONAL
We use zero conditional sentences to
talk about things that are generally or
always true.
If the condition shown by the dependent
clause is fulfilled, then the result shown
by the main clause will be true. This kind
of sentence uses the simple present
tense in both - the if-clause and the main
clause.
If you stay in water for a long time,
your skin will wrinkle.
If you mix red and green, you get
brown.

3. We use first conditional sentences to talk
about situations that are real they tell us of
events that may occur in the future, if
certain conditions are fulfilled. In this kind
of sentence, the if-clause is in the simple
present tense, and the main clause is in the
simple future tense.
1. If Arjun catches the 7 a.m. bus, he will
reach Agra by 2 p.m.
2. If Ranjana has enough money, she
will buy a pair of new shoes.
3. You will look funny if you cut your
hair very short.
4. If we reach the cinema hall by eleven,
we might get tickets.
FIRST
CONDITIONAL

4. GOOD TO KNOW
In a conditional sentence, the if-clause may come before or after the main clause. When
the if-clause comes before the main clause, it is separated from the main clause with a
comma.
No comma is required when the if-clause comes after the main clause.
If Malti has time today, she will go shopping.
or
01

5. SECOND
CONDITIONAL
We use second conditional sentences to
talk about hypothetical, unreal or
impossible situations. In such a sentence,
the if-clause is in the simple past tense.
The main clause has the modals would (to
express intension), could (to express
ability) or might (to express possibility).
1. If Kritagya had a yacht, he would
sail the seven seas.
2. If Anupam spoke five modern
language, he could work anywhere in
the world.
3. If you didn’t tell lies all the time,
people might trust you.

6. WATCH OUT!
In the second conditional, if the if-clause has the verb be, use the past form,
were, not was.
If I was you, I would first discuss the plan with others. 
If I were you, I would first discuss the plan with others.

7. THIRD CONDITIONAL
The third conditional is used to talk about a
hypothetical situation or condition in the past
which would have led to a different situation
in the present. In such a sentence, the if-
clause is in the past perfect or past perfect
continuous tense. The main clause has
could/would/might/should + (not) have + past
participle form of the verb.
If Himesh had not eaten so much, he
would not have fallen sick.
The present reality is that Himesh has fallen
sick. The reality of the past is that he ate too
much but the speaker talks about what might
have happened if Himesh had not eaten so
much.

8. Shaila would have missed the train if she hadn’t taken a taxi to the station.
The present reality is that Shaila caught the train. The reality of the past is that she
took a taxi. But the speaker talks about what might have happened if Shaila had not
taken a taxi.
If Shaan had watered the plants regularly, they might not have died.
The speaker talk about what might have happened if Shaan had watered the plants
Lana could have won the competition if she had trained harder.
The speaker talks about what might have happened if Lana had trained harder.

9. UNLESS, SHOULD AND
HAD
In some cases conditional sentences can be
formed using unless, should or had instead of if.
Unless you have a doctor’s prescription, you
cannot buy these medicines.
This sentence can be rewritten using if.
If you don’t have a doctor’s prescription, you
cannot buy these medicines.
Be careful when using unless. Never use don’t with
unless because the negation is already present in
unless.
Unless you don’t know the password. . . 
Unless you know the password. . . 
If you don’t know the password. . . 
Should can also be used to form conditional
sentences.
Should you need any assistance, please call us on
the given number.

10. This sentence can be rewritten using if.
If you need any assistance, please call us on the given number.
Remember, we use unless to describe real or possible situations.
Had can be used in place of if in the third conditional in formal situations.
Had Monty asked me, I would have told him not to go.
The present reality is that Monty has gone. The reality of the past is that he did not ask
the speaker. But the speaker talks about what might have happened if Monty had asked
her/him. This sentence can be rewritten using if.
If Monty had asked me, I would have told him not to go.
Notice that there is no change in the main clause when the sentence is written with if.
Here are a few more examples.
Had the film not been so violent, we might have watched it till the end
If the film had not been so violent, we might have watched it till the end.
Had the fishermen not returned, they would have been caught in the storm.
If the fishermen had not returned, they would have been caught in the storm.