How do I use the imperfect subjunctive?

The imperfect subjunctive is a fantastic way to pick up the extra marks needed for the top grade at A level, esepcially when used in 'Si' clauses' however it is one of the most complex grammatical structures. 

Your starting point is always the third person plural (they) preterite form - this will be your stem! For example, the verb tener in the third person plural preterite is 'tuvieron'. This means that our stem for this verb will be 'tuvie'.

To make your stem agree in the imperfect subjunctive (remember the stem will always be the same for forms), you then need to add the endings of the imperfect subjunctive. The spanish actually use two different endings and grammatically there's no difference between them - it's just a matter of preference! These endings are, in the 'yo' form 'ra' (slightly more common) and 'se'

the endings are as follows:

yo 'ra'   OR 'se'

tú: 'ras' OR 'ses'

él, ella, usted: 'ra' OR 'se'

nosotros: 'ramos' OR 'semos'

vosotros: 'rais' OR 'seis'

ellos: 'ran' OR 'sen'

NB: When using the 'nosotros' form, make sure you add a tilde on the vowel that comes immeditaely before the subjunctive ending: for example 'tuviéramos

Again, which form you prefer is entirely personal preference, so for the purpose of our example I shall use both.

The stem of tener being 'tuvie' as we have already worked out, to find our imperfect subjunctive we then add the agreeing ending. For example if I wanted to say 'If I had the opportunity to go the beach' I would apply the yo form to my stem.

therfore it would be: 

'Si tuviera la oportunidad, iría a la playa

Or using the alternative endings:

´Si tuviese la oportunidad, iría a la playa´