Subjunctive: Part I

The Forms of the Present Subjunctive / Las formas del presente del subjuntivo

	present indicative	PRESENT SUBJUNCTIVE
ayudar poner seguir	yo ayud-ø   yo pong-ø   yo sig-ø	ayude ayudes ayude ayudemos ayudéis ayuden ponga pongas ponga pongamos pongáis pongan siga sigas siga sigamos sigáis sigan

In order to form the present subjunctive, use the first person singular of the present indicative –the yo form–, remove the -o, and add endings in -e for -ar verbs, and endings in -a for -er and -ir verbs. This change of vowel may involve some spelling changes:
pag-ø  pague busc-ø  busque empiez-ø  empiece

• Stem-changing verbs in -ar and -er change their stems in the same way and in the same cases as in the present indicative:

piense vuelva

pienses vuelvas

piense vuelva

pensemos volvamos

penséis volváis

piensen vuelvan

• Stem-changing verbs in -ir, whatever the change that occurs in the present indicative, change the stem of thenosotros and vosotros forms of the present subjunctive from e to i and from o to u. (see complete rules.)

muera sienta pida

mueras sientas pidas

muera sienta pida

muramos sintamos pidamos

muráis sintáis pidáis

mueran sientan pidan

Only six verbs do not follow the rules above to form the present subjunctive:

ir  →  vaya, vayas, vaya, vayamos, vayáis vayan ser  →  sea seas sea seamos seáis sean estar  →  esté estés esté estemos estéis estén saber  →  sepa sepas sepa sepamos sepáis sepan haber  →  haya hayas haya hayamos hayáis hayan (subjunctive for hay) dar  →  dé des dé demos deis den

Subjunctive?

All the verbs we have studied so far have been in the Indicative Mood because they indicate states or actions that are presented as factual. The Subjunctive Mood is used, mostly in dependent clauses, after verbs that suggest non-factual events, such as indirect commands, doubts, subjective perception, etc. Compare the following two groups of sentences:

Presented as factual (indicative):	Desired, doubted (subjunctive):
I insist that he is here. Insisto en que está aquí.	I insist that he be here. Insisto en que esté aquí.
I believe he did it. Creo que lo hizo.	I demand that he do it. Exijo que lo haga.
I know he is here. Sé que está aquí.	I doubt he'll be here. Dudo que esté aquí.

Source and Original website + exercises here.