Present
Stem-changing verbs have a change in spelling and pronunication in the stem in all forms except the nosotros and vosotros. The change occurs in the stressed syllable of the conjugated verb which is also the last syllabus of the infinitive. All stem-changing verbs are noted in dictionary listings by indicating the change in parentheses. There are four categories: e – ie, o – ue, e – i, and u – ue (jugar is only the only verb of such a category)
| pensar (ie) | volver (ue) | pedir (i) |
| pienso, piensas, piensa, pensamos, pensáis, piensan | vuelvo, vuelves, vuelve, volvemos, volvéis, vuelven | pido, pides, pide, pedimos, pedís, piden |
Stem-changing verbs that also have irregular yo form include: decir – digo, tener – tengo, venir – vengo.
Preterite
Stem-changing verbs ending in -ir only have a stem change in the 3rd person singular and plural.In dictionary listings the second vowel or combination after a verb refers to a change in preterit (also present participle and present subjunctive).
| dormir (ue, u) | mentir (ie, i) | vestirse (i, i) |
| dormí, dormiste, d-u-rmió, dormimos, dormisteis, d-u-rmieron | mentí, mentiste, m-i-ntió, mentimos, mentisteis, m-i-ntieron | me vestí, te vestiste, se v-i-stió, nos vestimo, sos vestisteis, se v-i-stieron |
Imperfect
None exists.
Present Participle
A. The -ir sten changers have a change in the stem: dormir (ue, u) – durmiendo, vestir (i, i) – vistiendo, sentir (ie, i) – sintiendo.
In dictionary listings the second vowel or combination after a verb refers to a change in present participle (also preterite and present subjunctive).
B. Verbs ending in a vowel + er/ir (except for a silent -u- as in seguir) take a -y- instead of -i- in the ending: leer – le-y-endo, destruir – destru-y-endo.
Past Participle
None exists.
Present Subjunctive
- All -ar and -er stem-changing verbs have the same changes as in the present indicative tense.
- All -ir stem-changing verbs have the same as in the present indicative tense except for the nosotros and vosotros forms, which require a different stem-change. It is a change which is second in dictionary listings. It also refers to a change in present participle and preterite.
- Certain verbs are regular but need spelling changes to preserve the pronunciation.
almorzar almuerce, almuerces, almuerce, almorcemos, almorcéis, almuercen sentir sienta, sientas, sienta, sintamos, sintáis, sientan dormir duerma, duermas, duerma, durmamos, durmáis, duerman pedir pida, pidas, pida, pidamos, pidáis, pidan pagar pague, pagues, pague, paguemos, paguéis, paguen elegir elija, elijas, elija, elijamos, elijáis, elijan sacar saque, saques, saque, saquemos, saquéis, saquen cazar cace, caces, cace, cacemos, cacéis, cacen
Imperfect Subjunctive
None, since all are based on 3rd person plural of the preterite.
Future
None exists.
Conditional
None exists.