Conditional Forms

• Zero conditionals

• First conditionals

• Second conditionals

• Third conditionals

• Common alternative forms

There are four common conditional forms; zero, first, second and third conditionals. The zero and first conditionals are sometimes called 'real' conditionals, whereas the second and third conditionals are often called 'unreal' conditionals. All four conditional forms are composed of two clauses; the conditional (if) clause and the result clause. When a conditional sentence starts with the conditional (if) clause, it is separated from the result clause by a comma. If the sentence begins with the result clause, it is not separated from the conditional (if) clause by a comma.

The zero conditional is used to talk about something that is generally true. It can be used, for example, to explain scientific facts. The Zero conditional explains that if (a) is true, then (b) is also true. The Zero conditional can refer to past or present facts.

Basic Construction:
(If + subject + present simple verb), (subject + present simple verb.)  =  (Conditional clause) , (result clause.)
Or
(Subject + present simple verb) + (if + subject + present simple verb.)  =  (Result clause) (Conditional clause.)

Examples:

• If it snows, I don't drive my car.

• The journey to London takes 30 minutes if you use the motorway.

'If' can often be replaced by 'When':

• When it snows, I don't drive my car.

The first conditional is used to talk about the consequences of future events which are (at least in the opinion of the speaker) realistic, possible or likely. The 'if' clause describes the future event and the result clause explains the possible or probable consequence of the action. The First Conditional can only refer to future events (things which have not happened at the time of speaking).

Basic Construction:
(If + subject + present simple verb) ,  (subject + will + verb.)
Or
(Subject + will + verb)  +  (if + subject + present simple verb.)

Examples:

• If he fails the exam, I will be surprised.

• If I win the lottery, I will buy a house in San Fransisco.

• I will look for a new job if my boss doesn't give me a pay rise.

First Conditional and the Imperative
When we talk about the future, we often give commands or instructions, using an imperative form (Stop talking!). We can use the first conditional form to give conditional instructions.

Examples:

• If you see Robert, tell him to come to my office.

• If you smoke in here, remember to open the windows first!

The second conditional is used to talk about the hypothetical consequences of future events which are, at least in the opinion of the speaker, unlikely, improbable, impossible or unrealistic. The 'if' clause describes the future event and the result clause explains the hypothetical consequences of the action. The Second Conditional can only refer to future events (things which have not happened at the time of speaking).

Basic Construction
(If + subject + simple past verb) ,  (subject + would + verb.)
Or
(Subject + would + verb) + (if + subject + simple past verb.)

Examples:

• If he failed the exam, I would be surprised.

• If I won the lottery, I would buy a house in San Fransisco.

• I would look for a new job if my boss didn't give me a pay rise.

The third conditional is used to talk about things that would have happened if events in the past were different. The third conditional only refers to the past and only refers to ideas or actions that are hypothetical and impossible. It is often used to express regret about actions in the past that the speaker would like to change. The 'if' clause describes the past event which did not happen, and the result clause explains the hypothetical consequences of the action.

Basic Construction
(If + subject + past perfect) , (subject + would + have + past participle)
Or
(Subject + would + have + past participle) + (if + subject + past perfect)

Examples:

• If I had known he was married, I wouldn't have gone to dinner with him.  (I didn't know, so I went to dinner with him.)

• You would have met my brother if you had come to my party.  (You didn't come to my party, so you didn't meet him.)

• If I had studied harder at University, I could have been a Lawyer.  (I didn't study hard, so I am not a Lawyer.)

• First Conditional
  'If' can often be replaced by 'Unless' (to give the meaning "If...not)
  'Will' can be replaced by another future form (Going to... or Present Perfect)
  'Will' can be replaced by other modal verbs (depending on meaning) including 'Can, May, Might, Shall, Should, Ought to, Need to.'

• Second Conditional
  'If' can often be replaced by 'When'
  'If' can often be replaced by 'Unless' (to give the meaning "If...not)
  'Would' can be replaced by other modal verbs (depending on meaning) including 'Could, Should, Ought to.'

• Third Conditional
  Typically, the third conditional does not change, though 'Could' can replace 'Would'. However, it is very common for the conditional clause of a Third Conditional to be added to the result clause of a Second Conditional, to form a "Mixed Conditional". In spoken English this is perfectly acceptable, provided the meaning of the sentence is not altered.