This document discusses different types of conditional sentences in English: - Zero conditional sentences describe things that always happen with the structure "if + simple present, simple present". - First conditional sentences describe possible or likely situations with the structure "if + present, will/can/may + verb". - Second conditional sentences describe unlikely or imaginary situations with the structure "if + past simple, would/could/might + verb". - Third conditional sentences describe impossible past situations with the structure "if + past perfect, would have + past participle". Conditional sentences can also use "should" to suggest uncertainty or improbability, and can be formally inverted by moving the subject after an auxiliary verb.

1. Conditional sentences
What would you do if you saw
a ghost in your house?
By Mercedes Ramos

2. ZERO CONDITIONAL
USE: It always happens
● If it rains, the ground gets
wet
● If you heat water to 100
degrees, it boils
Simple present
if + simple present
If + simple present,
simple present

3. FIRST CONDITIONALCONDITIONAL
●
USE: It is possible or easy to happen
●
STRUCTURE: If + present simple, will + verb
, can
, may
, imperative verb
If you come early, we will go to the museum
If you come early, we can go to the museum
If you don't come late, you may come in
If you come late, don't make any noise

4. SECOND CONDITIONAL
●
USE: It is imaginary or difficult to happen
●
STRUCTURE: If + simple past, would + verb
, could + verb
, might + verb
If I were you, I wouldn't believe it
If you saw an injured pet in the street, you could take it home
If you were afraid, you might ask for help

5. THIRD CONDITIONAL
●
USE: It is used for impossible actions because it refers to
the past
●
STRUCTURE: If + past perfect, would have + past
participle
If + past perfect, could / might + past participle.
If you had come yesterday, you would have met my father
If you had been frozen, could you have run?
If you had wanted, you might have come with us

6. SHOULD IN CONDITIONAL SENTENCES
●
By using should in the if-clause we are suggesting that
something is unlikely or not particularly probable.
● If + subject + should + verb, subject + will + verb
, subject + can + verb
, subject + may + verb
, verb / don't + verb
If she should come, we will make a cake
If you should visit your aunt, buy her a present
If she should arrive, don't tell her any bad news

7. INVERSION IN CONDITIONAL SENTENCES
In formal English, conditional sentences can be formed by
inversion of the subject and the auxiliary verb. In
such sentences, if is removed.
Should he fail, don't tell him
Were I cleverer, I would be happier
Had I met him, we would have been friends
Had we gone, we wouldn't have had an argument