In English grammar there are four main types of conditional sentences and they can be used to express facts, or hypothetical situations and their consequences. Each type has different meaning and distinctive pattern.

The four types are: Zero, Type 1, Type 2 and Type 3 conditional sentences. There is also another type called Mixed.

First, we’ll take a look at the Zero Conditional.

Conditional sentences – Zero Conditionals

This type of conditional sentence can be used to express general truths, when the situation being referred to is real or possible. Also use this type to give instructions.

Conditional sentences consist of two clauses (two parts). The Zero conditional follows the structure below.

	Conditional clause (Condition)	Main clause (Consequence)
Structure:	If + Present simple,	Present simple
Example:	If you heat water,	it boils.
Example:	If you do not water your flowers,	they die.

Note:

When the sentence starts with if, use comma between the clauses. In other words when you start with the condition, separate the clauses with comma. When the consequence comes first no need to use comma.

We can start the sentence with the main clause (Consequence) too.

	Main clause (Consequence)	Conditional clause (Condition)
Structure:	Present simple	if + Present simple
Example:	Flowers die	if you don’t water them.
Example:	Answer the phone	if it rings.

Note:

we didn’t use comma between the clauses.

Type 1 Conditional

Use the first conditional when you want to say (or when you believe) that something is true. It is also used to say that certain actions are likely to happen in the present or future.

	Conditional clause (Condition)	Main clause (Consequence)
Structure:	If + Present simple,	Future tense
Example:	If I see her,	I’ll call you.
Example:	If I have time,	I will write you a postcard.

You can also use these type of conditional sentences with imperatives in the main clause. For example:

Buy me a car and I’ll love you.

Type 2 Conditional

This type of conditional sentence is used to talk about imaginary or improbable situations, situations that are unlikely (but not impossible) to happen. Although the past tense is used in the sentence, the speaker refers to something untrue or unreal in the present.

	Conditional clause (Condition)	Main clause (Consequence)
Structure:	If + Past tense,	would + Infinitive
Example:	If I won the lottery,	I would buy a big house.
Example:	If I were you,	I wouldn’t eat so much.

Note:

Nowadays “If I were…” and “If I was…” are used interchangeably, although “If I were…” is considered grammatically correct and more acceptable, particularly in formal written contexts.

Type 3 Conditional

The third conditional can be used to talk about situations or events that cannot be changed because they happened in the past.

	Conditional clause (Condition)	Main clause (Consequence)
Structure:	If + Past perfect,	would/might/could have + Past perticiple
Example:	If we had brought a map,	we wouldn’t have got lost.
Example:	If you had driven slowly,	you wouldn’t have caused an accident.

In the first example we didn’t bring a map and as a result we got lost.
In the second example you didn’t drive slowly and as a result you did cause an accident.

Mixed Conditionals

A mixed conditional is a type of conditional sentence that contain a mixture of a third and second conditional sentence.It connects a completed past event or situation with a present result.

	Conditional clause (Condition)	Main clause (Consequence)
Structure:	If + Past perfect,	present conditional
Example:	If I had studied more,	I would have a better job now.
Example:	If I hadn’t had an accident,	I would go to your wedding.

Note:

You may use other words instead of “if”. These are: when, unless, in case, Providing (that)…, provided (that)…, On condition that etc.