The unrealA tense that expresses a hypothetical situation. E.g.: I wish you were here. (or hypotheticalUnreal, imagined.) 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.s have the form of the past simple or the past perfectThe aspect expressing completion. E.g.: He’s finished university. but they refer to present or past timeA concept which is related to our perception of reality; that part of existence which is measured in seconds, minutes, hours, days, weeks, etc., respectively. They are 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 which hypothesise an imaginary present or an impossible past situation.

I wish you were here. (an imaginary present situation, because you are not here)
If I had gone to bed earlier, I wouldn’t have overslept. (an impossible past situation, because I didn’t go to bed earlier)

This applies to the subordinate clauses in the second and third conditionals, wish/if only, as if/as though, it’s (high) time, would rather/would sooner etc. sentences.

Guiding questions: conditionals and unreal tenses
Conditionals and unreal tenses IF-sentences and conditionals