The past perfectThe aspect expressing completion. E.g.: He’s finished university. subjunctive has the same form as the past perfect tenseA grammatical category that is marked by verb inflection. To express when an event or action happens in time or when a state exists, we use tenses..

had + past participle

It is used in subordinate clauseA clause that cannot be a sentence in itself. It is joined with a main clause. E.g.: I wouldn’t go there if I were you. ("if I were you") When I arrived he was surfing. ("when I arrived")s and expresses an unrealA tense that expresses a hypothetical situation. E.g.: I wish you were here. past situation:

The present subjunctive has the same form as the infinitive without to for all persons, including third person singular. It is used:

I would prefer it if it stopped snowing.

This is a second conditional sentence.

subject 1 + would rather/sooner + clause (subject 2 + past perfect)

I’d rather we had never met. (= If only we had never met.)
What would you rather I had written? (= What do you wish I had written?)

subject 1 + would rather/sooner + clause (subject 2 + unreal tense)

To express ability or possibility could + perfectThe aspect expressing completion. E.g.: He’s finished university. infinitive is used in the IF-clauseA group of related words containing a subject and a verb. of third conditional sentences.

If he could have got to the airport on time, he would not have missed the flight.

The auxiliaryA helping verb used with main verbs to express mood, voice and tense. E.g.: I can't stand when I am disturbed. ("can", "am") could is used here to express permission or ability.

I'd go to the beach with you if I could swim.

In the if-clauseA group of related words containing a subject and a verb. of the first conditional we can use should (to express that the condition is less likely), can (permission or ability), will or would (willingness, insistence and refusal), must (obligation) or may (permission).

The auxiliaryA helping verb used with main verbs to express mood, voice and tense. E.g.: I can't stand when I am disturbed. ("can", "am") may is used to express contrast.

You may be right, but that is no excuse for shouting like this. (Although you are right, that is...)

Try as somebody may (present reference) and try as somebody might (past reference) mean however hard I try/tried...

If superlative adjectiveA part of speech that modifies, qualifies or restricts a noun or a pronoun. E.g.: The apples are ripe. ("ripe")s (especially the first, the last) are used, an infinitive structureThe way in which the parts of a sentence, clause or expression are arranged. E.g.: make somebody + infinitive in "The teacher made me rewrite the composition." can replace a defining relative clauseA group of related words containing a subject and a verb..

Geoffrey was the last to understand the joke. (= Geoffrey was the last person who understood the joke.)

If we want to express an actionA general term expressing that somebody or something does something in the passive voiceThe form of the transitive verb that shows whether the subject acts (active voice) or is acted upon (passive voice)., a passive infinitive is used: