Se Eu Tivesse: Past Subjunctive

The past subjunctive (imperfeito do conjuntivo) describes situations that are imagined or contrary to fact right now.

Take the eles form of the preterite, drop -ram and add -sse: falaram → falasse, tiveram → tivesse, foram → fosse. The endings are -sse, -sses, -sse, -ssemos, -ssem, and the nós form carries an accent: falássemos, tivéssemos, fôssemos.

• Se + past subjunctive, then the conditional or, in everyday speech, the imperfect: Se eu tivesse tempo, ia contigo. (If I had time, I would go with you.)
• It also follows como se (as if), quem me dera que (I wish) and queria que (I'd like... to).

For conditions about the past, use tivesse + past participle: Se eu tivesse sabido, tinha ajudado. (If I had known, I would have helped.)