Irregular Subjunctive Ending?
I have noticed from time to time what appears to be an irregular rule or construction for forming second-person subjunctive verbs.
A most recent example:
Yo quería que tú me enseñases. (I want you to teach me).
I understand the need for the subjunctive here, but why add the extra -es on the end? Following the basic rule, "enseñes" would have been my assumption.
Can anyone tell me if this is a rule that I was not aware of? Perhaps verbs ending in -ñar just need to add the extra -es on the subjunctive form while leaving the last vowel in the root in the normal indicative form?
Any help would be appreciated! Thanks!
6 Answers

Did anybody look it up in our verb conjugation table?
It's right there under "Imperfect Subjunctive #2".
http://www.spanishdict.com/conjugate/enseñar
The #2 form of the imperfect subjunctive means exactly the same thing as the #1 form. As I understand it, it's primarily used in fancy literary situations and is uncommon in day to day use.
That´? the imperfect subjunctive I think. It? the exact same as the "ra" form, apparently they?e both common in Spain and South America and anyone I ask says they can´t sense any difference.
yo -se comprase vendiese tuviese fuese
tú -ses comprases vendieses tuvieses fueses
él/ella/ustedes -se comprase vendiese tuviese fuese
nosotros/-as -semos comprásemos vendiésemos tuviésemos fuésemos
vosotros/-as -seis compraseis vendieseis tuvieseis fueseis
ellos/ellas/ustedes -sen
comprasen vendiesen tuviesen fuesen
(conjugations from the book "Intermediate Spanish A Grammar and Workbook" published by Routledge.)
For the imperfect subjunctive, I would say:
(Yo) quería que (tú) me enseñaras. (I wanted you to teach me.)
I have never seen that second version of the imperfect subjunctive. Perhaps it is literary?
According to Paralee in lesson 3.11 - Hopes and Dreams with the Imperfect Subjunctive:
1) Form the imperfect subjunctive stem using the 3rd person plural form of the preterit.
2) All imperfect subjunctive verbs use the same endings.
3) The imperfect subjunctive have 2 different ending sets.
4) The -ra endings ( that is: -ra, -ras, -ra, - ramos, - rais, and -ran) are common in all Spanish speaking countires.
5) The second is used in texts in Spain. ( that is; -se, -ses, -se, -semos, -seis, and -sen)
Look at this post
I think this form is more common in Spain,as Spainards I have talked to used it.