The Spanish imperfect subjunctive resembles the English simple past because it is used to express past doubts, wishes, and emotions as well as to convey politeness and construct conditional clauses. There are two forms (cantara or cantase) that can be used interchangeably. Following are the primary uses of the Spanish imperfect subjunctive:

-To express politeness

La directora del colegio quisiese/quisiera hablar con usted.

– To describe past actions in subordinate clauses

El dentista sugirió que me cepillara/cepillase los dientes con una pasta medicada.

-In conditional clauses beginning with the conjunction si

Si llegaras/llegases antes del viernes, podemos irnos de campamento.

-To express the negative belief of a certainty conveyed in the imperfect of the indicative mood.

Positive imperfect indicative: Juanita cantaba cuando estaba alegre

Negative imperfect subjunctive: No creo que Juanita cantase/cantara cuando estaba alegre.