Conditionals

The Zero Conditional

The zero conditional takes two present simple verbs, one in the 'if' clause and one in the main clause:

Form: If + present simple, .... present simple.

This conditional is used when the result invariably follows. Water that reaches 100 degrees always boils; the statement is a matter of fact. The reference is general rather than to one particular occasion, and the 'if' clause always produces the main clause.

In this conditional, 'if' can normally be replaced by 'when' with no change of meaning.

For example: If water reaches 100 degrees, it boils. (This holds without exception; no other outcome is possible.) If I eat peanuts, I am sick. (This may be true of me alone rather than of everyone, but it holds every time I eat peanuts.)

Further examples:

The First Conditional

The first conditional takes the present simple after 'if' and the future simple in the main clause:

Form: if + present simple, ... will + infinitive

It refers to what may happen in the future. The future is of course unknown, but this pattern describes outcomes that are entirely plausible.

Further examples:

First conditional compared with zero conditional:

The first conditional describes one particular situation, whereas the zero conditional describes what happens in general.

Zero conditional: if you sit in the sun, you get burned. (The reference is to every occasion on which a person sits in the sun. Burning is the natural consequence.)

First conditional: if you sit in the sun, you'll get burned. (The reference is to what will happen today. Another day might be different.)

First conditional compared with second conditional:

The first conditional describes what the speaker considers likely to happen, whereas the second conditional describes what the speaker does not expect to happen at all. The distinction is subjective and rests on the speaker's own view.

First conditional: If she studies harder, she'll pass the exam. (I consider it possible that she will study harder and therefore pass.)

Second conditional: If she studied harder, she would pass the exam. (I do not expect her to study harder, so I do not expect her to pass.)

The Second Conditional

The second conditional takes the past simple after 'if', then 'would' and the infinitive:

Form: if + past simple, ...would + infinitive

'Were' may replace 'was' with 'I' and 'he / she / it'. This is largely confined to formal writing.

It has two uses.

First, it refers to future situations that are unlikely to come about, including those that are purely imagined.

Second, it refers to a present situation that is impossible because it is not the case. The examples below illustrate this:

How does this differ from the first conditional?

The second conditional differs from the first in presenting the situation as considerably less likely.

Second conditional: If I had enough money, I would buy a house with twenty bedrooms and a swimming pool. (I am unlikely ever to have that much money. The situation is imagined rather than real.)

First conditional: If I have enough money, I'll buy some new shoes. (Having enough money for shoes is a far more realistic prospect.)

The Third Conditional

The third conditional takes the past perfect after 'if', then 'would have' and the past participle in the second part of the sentence:

Form: if + past perfect, ...would + have + past participle

It refers to the past. It describes a situation that did not occur and imagines what would have followed from it.