The conjugation of the subjunctive imperfect active follows a simple rule. The verb in its infinitive form, that is, the second principle part, (amāre, to love, for example) simply has the active personal endings (-m/ō, -s, -t, -mus, -tis, -nt) added:
the passive voice is formed by the addition of passive personal endings (-r, -ris (-re), -tur, -mur, -minī, -ntur) onto the infinitive stem
tu amārēris (-re)
== Application ==
The imperfect subjunctive is only used for complex syntactic constructions; cum clauses and indirect questions and the like. Rarely, if ever, does it stand alone.
=== Because/Cum ===
One application is in its use with 'cum' in the sense of 'because' as a clause. e.g.
Diutius cum sustinere nostrorum impetus non possent, Helvetii se in montem receperunt.
When(Because) the Helvetis could not sustain/resist our attacks for long, they retreated to the mountains.