conditionals

CONDITIONALS
The zero conditional is a structure used for talking about general truths — things which always happen under certain conditions. This page will explain how the zero conditional is formed, and when to use it.

1. The structure of a zero conditional sentence

A zero conditional sentence consists of two clauses, an “if” clause and a main clause (In most zero conditional sentences you can use when or if and the meaning will stay the same.):

“if” clause	main clause
If you heat water to 100 degrees,	it boils.

If the “if” clause comes first, a comma is usually used. If the “if” clause comes second, there is no need for a comma:

main clause	“if” clause
Water boils	if you heat it to 100 degrees,

We use the same verb form in each part of a zero conditional: the simple present tense:

“if” clause	if + subject + simple present verb
main clause	subject + simple present verb

2. Using the zero conditional

The zero conditional is used to talk about things which are always true — such as scientific facts and general truths:

Example

Explanation

If you cross an international date line, the time changes.

This always happens — every time you cross a date line.

If it rains, the grass gets wet.

This is basically always true — the rain makes the grass wet.

Wood doesn't burn if there is no air.

This is a scientific fact — wood needs air in order to burn. No air = no fire.

THE SECON CONDITIONAL

The second conditional (also called conditional type 2) is a structure used for talking about unreal situations in the present or in the future. This page will explain how the second conditional is formed, and when to use it.

The structure of a second conditional sentence

Like a first conditional, a second conditional sentence consists of two clauses, an “if” clause and a main clause:

“If” clause	Main clause
If I had a million dollars,	I would buy a big house.

If the “if” clause comes first, a comma is usually used. If the “if” clause comes second, there is no need for a comma:

Main clause	“If” clause
I would buy a big house	if I had a million dollars.

We use different verb forms in each part of a second conditional:

“If” clause	if + subject + simple past verb*
Main clause	subject + would + verb

*Note that this "simple past" form is slightly different from usual in the case of the verb BE. Whatever the subject, the verb form is "were", not "was": If I were rich, I'd buy a big house.

Using the second conditional

The second conditional is used to talk about things which are unreal (not true or not possible) in the present or the future -- things which don't or won't happen:

Example	Explanation
If I were you, I would drive more carefully in the rain.	I am not you — this is unreal.
Paula would be sad if Jan left.	Jan will not leave — that's not going to happen.
If dogs had wings, they would be able to fly.	Dogs don't have wings — that's impossible.

THIRD CONDITIONAL

The third conditional (also called conditional type 3) is a structure used for talking about unreal situations in the past. This page will explain how the third conditional is formed, and when to use it.

The structure of a third conditional sentence

Like the other conditionals, a third conditional sentence consists of two clauses, an “if” clause and a main clause:

IF clause	main clause
If I had studied harder,	I would have passed the exam.

Explanation: I failed the exam, because I didn't study hard enough.
If the “if” clause comes first, a comma is usually used. If the “if” clause comes second, there is no need for a comma:

main clause	IF clause
I probably would have passed the exam	if I had studied harder.

We use different verb forms in each part of a third conditional:

IF clause	if + subject + past perfect verb*
main clause	subject + would (OR could, OR might) have + past participle

*The past perfect is formed with the auxiliary verb “had”, and the past participle (or third form) of the verb.
Note also that third conditional forms can be contracted:

Full form	If I had studied harder, I probably would have passed the exam.
Contracted form	If I'd studied harder, I probably would've passed the exam.

Using the third conditional

The third conditional is used to talk about things which did not happen in the past. If your native language does not have a similar construction, you may find this a little strange, but it can be very useful. It is often used to express criticism or regret:

Example	Explanation
If you had driven more carefully, you would not have had an accident.	Criticism: You had an accident because you didn't drive carefully enough.
If we had played a little better, we could have won the game.	Regret: We didn't play well, so we lost the game.
If you had saved your money, you could have bought a computer.	Criticism: You didn't save your money, so now you can't afford a computer.
If it had snowed, we could have gone skiing.	Regret: It didn't snow, so we couldn't go skiing.