Introduction to the Subjunctive

verb mood used to say what one person does or doesn’t want, tell, suggest, or recommend someone else to do.

Ejemplo: Quiero que me hagas un favor. (I want you to do me a favor.)

Will (verbs of volition such as preferir (ie, i)/to prefer)

Emotion (verbs of emotion such as sentir (ie, i)/to regret or alegrarse de/to be happy about)

Desire (verbs such as querer (ie)/to want) 

Doubt (verbs such as dudar/to doubt)

Impersonal expressions (es posible/it is possible)

Negative (neg. antecedents like nadie/no one)

Generalized expressions (Ojalá/hopefully, en caso de que/in the event that )

One way to ask someone to do something, or to express a desire that another person do something, is to use querer + que + subjunctive

Ejemplo: Mi madre quiere que mi hermano la lleve al mercado. (My mother wants my brother to take her to the market.)

Same as formal (Ud. & Uds.) commands

yo form of present indicative, drop -o, add opposite vowel ending

ejemplos: hable/diga/coma/cierre

servir (i, i) --> sirva, sirvas, sirva, sirvamos, sirváis, sirvan

dormir (ue, u) --> duerma, duermas, duerma, durmamos, durmáis, duerman

use change AFTER the comma for nosotros and vosotros forms only, ex: me divierta, nos divirtamos (ie, i)

dar-> dé, des, dé, demos, deis, den

ir-> vaya, vayas, vaya, vayamos, vayáis, vayan

saber-> sepa, sepas, sepa, sepamos, sepáis, sepan

haber-> haya, hayas, haya, hayamos, hayáis, hayan

estar-> esté, estés, esté, estemos, estéis, estén

ser-> sea, seas, sea, seamos, seáis, sean

Hay mucha gente en la fiesta. (There are a lot of people at the party) (INDICATIVE MOOD--> fact)

No quiero que haya mucha gente en la fiesta. (I don't want there to be a lot people at the party.) (SUBJUNTIVE MOOD--> desire)