How the irregularity works
Many of the most common verbs have their own stem in the pretérito indefinido. The endings are the same for almost all of them, so mostly you just have to learn the new stems. English does something similar (go → went, have → had), but Spanish is more systematic: once the stem is replaced, the endings are shared.
The shared endings
These endings apply to almost every verb with a new stem (not to ser and ir). The stress falls on the stem, so tuve and tuvo have no written accent.
Endings for the irregular verbs
| Person | Ending | tener |
|---|---|---|
| yo | -e | tuve |
| tú | -iste | tuviste |
| él/ella/usted | -o | tuvo |
| nosotros/as | -imos | tuvimos |
| vosotros/as | -isteis | tuvisteis |
| ellos/ellas/ustedes | -ieron | tuvieron |
Example: tener (to have), stem tuv-
Stress - regular against irregular
habló
he/she spoke (regular, stress on the ending)
tuvo
he/she had (irregular, stress on the stem)
The most important new stems
Stems at a glance
| Infinitive | Stem | yo |
|---|---|---|
| tener (to have) | tuv- | tuve |
| estar (to be) | estuv- | estuve |
| poder (can, to be able) | pud- | pude |
| poner (to put) | pus- | puse |
| saber (to know) | sup- | supe |
| querer (to want) | quis- | quise |
| hacer (to do, make) | hic- | hice |
| venir (to come) | vin- | vine |
| decir (to say) | dij- | dije |
| traer (to bring) | traj- | traje |
infinitive, new stem and yo form
The new stems in a sentence
Tuve que trabajar hasta tarde.
I had to work until late.
Estuvimos en la playa todo el día.
We were at the beach all day.
No pude dormir bien anoche.
I couldn't sleep well last night.
¿Qué hiciste el fin de semana?
What did you do at the weekend?
Me dijeron la verdad.
They told me the truth.
Ayer vi una película muy buena.
Yesterday I saw a very good film.
ser and ir - one set of forms
ser (to be) and ir (to go) have exactly the same forms in the indefinido and do not follow the endings above. English keeps was and went apart, so this feels odd at first, but the sentence gives it away: fui a + place means I went, fue + noun or adjective means was.
ser / ir
| Person | ser / ir |
|---|---|
| yo | fui |
| tú | fuiste |
| él/ella/usted | fue |
| nosotros/as | fuimos |
| vosotros/as | fuisteis |
| ellos/ellas/ustedes | fueron |
one form, two meanings
fue = was OR went
Fue un día fantástico.
It was a fantastic day. (ser)
Ayer fui al cine.
Yesterday I went to the cinema. (ir)
