Preterite Stem Changes in Common IR Verbs
Pidió and durmieron hide a smaller stem change inside third-person preterite forms. Limit the shift to the correct forms of pedir, dormir, and similar IR verbs.
Learning objective
Apply E to I and O to U changes in third-person preterite forms of frequent IR verbs.
A preterite stem change is a vowel change inside the main part of certain IR verbs when they describe completed past actions. Unlike present-tense stem changes, this past pattern appears only in the third-person forms: the forms for él, ella, usted, ellos, ellas, and ustedes.
For E-to-I verbs such as pedir, repeat the regular IR preterite endings but change the stem vowel in pidió and pidieron. The other forms keep the original vowel: pedí, pediste, pedimos, and pedisteis. In much of Latin America, ustedes pidieron supplies the everyday plural you form; vosotros pedisteis is used mainly in Spain.
For O-to-U verbs such as dormir, the corresponding forms are durmió and durmieron. Again, only the third person changes: dormí, dormiste, dormimos, dormisteis, durmió, durmieron. Keeping the change limited prevents the incorrect form duermí, which imports the present-tense pattern.
Use these forms inside a real sequence rather than as an isolated chart. Anoche pedimos comida, pero Elena pidió una sopa y después durmió temprano connects a group order, one person’s choice, and a finished result. Each verb has a clear subject and a completed place in the story.
Other frequent IR verbs follow the same restricted pattern: servir gives sirvió and sirvieron, while preferir gives prefirió and prefirieron. Learn one useful sentence with each verb, then check two questions: is the action completed, and is the subject third person? Only when both answers are yes does this change apply.
Examples
La camarera sirvió la cena y después el cliente pidió la cuenta.
The server served dinner, and then the customer asked for the bill.
Sirvió and pidió link two completed third-person actions.
Mis primos durmieron ocho horas después del viaje.
My cousins slept for eight hours after the trip.
The plural third-person form changes O to U inside the stem.
Pedimos dos cafés, pero Ana pidió té.
We ordered two coffees, but Ana ordered tea.
Pedimos stays unchanged; pidió has the E-to-I change.
¿Prefirieron caminar o tomaron el autobús?
Did they prefer to walk, or did they take the bus?
The question asks about two finished alternatives.
Common mistake
- Instead of
- Ayer yo pidí una ensalada y mis amigos pedieron sopa.
- Try
- Ayer yo pedí una ensalada y mis amigos pidieron sopa.
The first-person form pedí keeps the original E, while the third-person plural form pidieron changes E to I. The change is not applied to every person, and the regular preterite ending still remains. Reading the subjects first—yo and mis amigos—makes the two choices easier to control.
Practice
Try it yourself
Complete this short account with the preterite of pedir, servir, and dormir: Anoche, Marta ___ pasta. El camarero ___ el plato a las ocho. Después de cenar, Marta y Luis ___ bien.