Spanish Present Subjunctive

One use of the subjunctive mood is to persuade someone to do something. If you were to call a friend only to discover that he is out, you might ask whoever answered the phone to take a message. In Spanish, such a sentence requires use of the subjunctive mood.

For example:

Dile que me devuelva mi libro mañana. 
Tell him to return my book to me tomorrow.

Sí señor, dígale por favor que lleve mi disco 
de los Ilegales a la escuela mañana. 
Yes sir, please tell him to bring my Ilegales 
CD to school tomorrow.

Notice that in each example the speaker is asking someone to do something. If the speaker were simply giving information then the subjunctive mood would not be used. The formation of these sentences of persuasion follows this pattern:

Persuasion verb + que + verb in subjunctive form

To form the present subjunctive you simply take the first person indicative form (e.g. hablo) and, with -ar verbs, change the -o ending to -e. For -er and -ir verbs, change the -o to -a.

hablar hablo hable
comer como coma
vivir vivo viva

To make the other forms of the present subjunctive you simply add the same endings (-s, -mos, -is, -n) as you used in the present indicative.

hablar hablo hable, hables, hable, hablemos, habléis, hablen
comer como coma, comas, coma, comamos, comáis, coman
vivir vivo viva, vivas, viva, vivamos, viváis, vivan

For -ar and -er stem-changing verbs, the pattern remains the same as it is for the present indicative: all forms change except nosotros and vosotros.

For example:
pida, pidas, pida, pidamos, pidáis, pidan
muera, mueras, muera, muramos, muráis, mueran

Most verbs that have irregular stems in the first person singular of the present indicative will keep that irregularity in all forms of the present subjunctive:

decir digo diga, digas, diga, digamos, digáis, digan
conocer conozco conozca, conozcas, conozca, conozcamos, conozcáis, conozcan

Finally, there are some verbs whose first person singular present indicative from does not end in -o. These verbs have the following present subjunctive form:

dar dé, des, dé, demos, deis, den
estar esté, estés, esté, estemos, estéis, estén
ir vaya, vayas, vaya, vayamos, vayáis, vayan
saber sepa, sepas, sepa, sepamos, sepáis, sepan
ser sea, seas, sea, seamos, seáis, sean

Now, let's look at some other examples of persuasion:

Juan quiere que vayamos a su casa. Juan wants us to go to his house.
Prefiero que me traigan su tarea al final de la clase. I prefer that you bring me your homework at the end of class.

Subjunctive Mood