Pluperfect Progressive - Conditional Sentences

Conditional Sentences

A conditional sentence usually contains two clauses: an if-clause or similar expressing the condition (the protasis), and a main clause expressing the conditional circumstance (the apodosis). In English language teaching, conditional sentences are classified according to type as first, second or third conditional; there also exist "zero conditional" and mixed conditional sentences.

A "first conditional" sentence expresses a future circumstance conditional on some other future circumstance. It uses the present tense (with future reference) in the condition clause, and the future with will (or some other expression of future) in the main clause:

If he comes late, I will be angry.

A "second conditional" sentence expresses a hypothetical circumstance conditional on some other circumstance, referring to non-past time. It uses the past tense (with the past subjunctive were optionally replacing was) in the condition clause, and the conditional formed with would in the main clause:

If he came late, I would be angry.

A "third conditional" sentence expresses a hypothetical (usually counterfactual) circumstance in the past. It uses the past perfect in the condition clause, and the conditional perfect in the main clause:

If he had come late, I would have been angry.

A "mixed conditional" mixes the second and third patterns (for a past circumstance conditional on a not specifically past circumstance, or vice versa):

If I knew Latin, I wouldn't have made that mistake just now.

If I had got married young, I would have a family by now.

The "zero conditional" is a pattern independent of tense, simply expressing the dependence of the truth of one proposition on the truth of another:

If Brian is right, then Fred has the jewels.

See also the following sections on expressions of wish and dependent clauses.