For me, the easiest way of forming the imperfect subjunctive in Spanish is to firstly start with the 3rd person plural form of the preterite. Once you have this, drop the -ron ending of the verb. This base can be used for all verbs, whether they are regular, irregular, stem-changing or spelling- changing. Then add one of the following endings, depending on the person: yo- ratú-rasél/ella/usted- ranosotros- ramos vosotros -raisellos/ellas/ ustedes- ranAnd there you have it! An example of where you might use this tense includes expressing hypothetical situations in the past. e.g. 'Si yo tuviera más dinero, compraría una casa muy grande'.