After having learnt how to conjugate the present subjunctive of regular Spanish verbs, (See Spanish present subjunctive. Regular verbs), let's now review how to conjugate irregular Spanish verbs in present subjunctive tense.

Let's choose an irregular verb. For example, Sentir. Sentir is irregular, because when we conjugate this verb in present tense indicative, its root "sent-" changes to "sient-" (e --> ie). Other similar irregular verbs are Venir, or Tener ("él viene", "él tiene").

The conjugation of these irregular verbs in present subjunctive is quite simple.

First thing we have to do: Conjugate the verb in present indicative:

Yo siento
Tú sientes
Él siente

Nosotros sentimos
Vosotros sentís
Ellos sienten

(Note: Can you see the irregularity? Infinitive: Sentir. Root: Sent-. Present tense indicative conjugation: Siento, sieiente, sentimos, sentís, sienten. The irregularity involves every person conjugated, except for first and second plural.)

Second step: change the endings:

Present Indicative	Present Subjunctive	Endings
Yo siento	Yo sienta	-o → -a
Tú sientes	Tú sientas	-es → -as
Él siente	Él sienta	-e → -a
Nosotros sentimos	Nosotros sintamos	-imos → -amos
Vosotros sentís	Vosotros sintáis	-ís → -áis
Ellos sienten	Ellos sientan	-en → -an

The easy part here is how the following persons change: first singular (yo), second singular (tú), third singular (él) and third plural (ellos). They change their vowels endings to "a". (About the second person plural (vosotros), instead of changing the ending vowel ("í") to "a", the vowel is in fact added to the present tense ending: -ís → áis.)

The rest (first and second plural persons (nosotros and vosotros)):
- change the vowel "e" in the root: from "e" to "í" (marked in red).
- their endings also change: from "í" to "a", for the first person plural , and from "í" to "áis", for the second person plural .

Listen to "sentir" in present indicative and present subjunctive

Sure it seems somehow difficult, but let's see another example. This time we'll choose another different irregular verb: Pensar.

First, we'll conjugate it in present tense indicative, as this tense we'll give us the clue to start conjugating the present subjunctive.

Present tense Indicative, verb Pensar:

Yo pienso
Tú piensas
Él piensa

Nosotros pensamos
Vosotros pensáis
Ellos piensan

So, from this point, we change ending vowels:

Present Indicative	Present Subjunctive	Endings
Yo pienso	Yo piense	-o → -e
Tú piensas	Tú pienses	-as → -es
Él piensa	Él piense	-a → -e
Nosotros pensamos	Nosotros pensemos	-amos → -emos
Vosotros pensáis	Vosotros penséis	-áis → -éis
Ellos piensan	Ellos piensen	-an → -en

Same as for the verb "Sentir", all persons, except first and second plural, take the irregular form "piens-".

Listen to verb "pensar" in present indicative and present subjunctive

The difference you can see in both verbs endings for the present subjunctive, is because the verb "Pensar" belongs to the first conjugation (Verbs ending in -ar) and the verb "Sentir" belongs to the third conjugation type. To refresh concepts:

	Present Indicative	Present Subjunctive
First conjugation verbs (-ar)	-a	-e
Second conjugation verbs (-er)	-e	-a
Third conjugation verbs (-ir)	-e	-a

The conjugation of irregular verbs for the first person singular (yo) is not as difficult as you may think. Verbs like "tener" (yo tengo), "venir" (Yo vengo) or "decir" (Yo digo).

To conjugate this type of irregular verbs, pay attention to the first person singular -present indicative- form. (Yo tengo, yo vengo or yo digo). Use this form as the model to conjugate all persons in present subjunctive, as follows:

Present Indicative (Verb decir): Yo digo
Present Subjuntive (Verb decir): Yo diga, tú digas, él diga, nosotros digamos, vosotros digáis, ellos digan.

Present Indicative (Verb venir): Yo vengo
Present Subjuntive (Verb venir): Yo venga, tú vengas, él venga, nosotros vengamos, vosotros vengáis, ellos vengan.

Present Indicative (Verb tener): Yo tengo
Present Subjuntive (Verb tener): Yo tenga, tú tengas, él tenga, nosotros tengamos, vosotros tengáis, ellos tengan

To learn more about Spanish verbs: The Big Red Book of Spanish Verbs with CD-ROM, Second Edition