A specific subset of -ir verbs shows a minor but persistent irregularity in the preterite: the stem vowel e shifts to i, but only in the third-person singular and plural forms. Pedir gives pedí, pediste, pidió, pedimos, pedisteis, pidieron. The first four forms keep the regular e; only pidió and pidieron show the change.
This pattern is more limited than it sounds. It only applies to -ir verbs that already stem-change in the present (either e→i like pedir, or e→ie like sentir). -ar and -er verbs are immune. Comer stays comió, comieron. Hablar stays habló, hablaron. The change is an -ir-only specialty inherited from Latin's vowel system.
When this rule applies — and when it doesn't
To apply this rule you need to know whether a given -ir verb is in scope. The criterion is simple: if the verb stem-changes in the present indicative (e→i or e→ie), it stem-changes in the third-person preterite (e→i). That's the full test.
So:
- In scope: pedir (pido → pidió), servir (sirvo → sirvió), repetir (repito → repitió), seguir (sigo → siguió), vestir (visto → vistió), sentir (siento → sintió), preferir (prefiero → prefirió), mentir (miento → mintió), divertirse (me divierto → se divirtió), consentir (consiento → consintió), reír (río → rió), freír (frío → frió), sonreír (sonrío → sonrió).
- Out of scope: escribir (escribo, no stem change → escribió), vivir (vivo → vivió), abrir (abro → abrió), subir (subo → subió). These are regular -ir verbs and keep the e (or whatever stem vowel) intact across the preterite.
Notice that preferir and sentir in the present diphthongize (prefiero, siento — e→ie), but in the preterite they collapse the diphthong to a single i (prefirió, sintió). The -ió ending is already palatal-influenced; Spanish doesn't pile a diphthong on top.
Pedir — the model
The textbook model is pedir. Same verb that headlines the present-tense e→i page; here it shows the same change in the preterite, but only in the third persons.
| Subject | Form | Stem |
|---|---|---|
| yo | pedí | ped- (regular) |
| tú | pediste | ped- (regular) |
| él / ella / usted | pidió | pid- (e→i) |
| nosotros / nosotras | pedimos | ped- (regular) |
| vosotros / vosotras | pedisteis | ped- (regular) |
| ellos / ellas / ustedes | pidieron | pid- (e→i) |
Le pedí dinero a mi padre para el alquiler.
I asked my dad for money for the rent.
Pidió el menú del día y un café con leche.
He ordered the lunch special and a coffee with milk.
Mis hijos pidieron pizza para cenar.
My kids asked for pizza for dinner.
¿Qué pedisteis en el restaurante de anoche?
What did you guys order at the restaurant last night?
The vosotros form is pedisteis — regular, with the e intact, just like yo, tú, nosotros. The shift to i happens only in the third person.
Servir, repetir, vestir — same shape
Three other common verbs follow the pedir pattern exactly.
| Subject | servir | repetir | vestir |
|---|---|---|---|
| yo | serví | repetí | vestí |
| tú | serviste | repetiste | vestiste |
| él / ella | sirvió | repitió | vistió |
| nosotros | servimos | repetimos | vestimos |
| vosotros | servisteis | repetisteis | vestisteis |
| ellos / ellas | sirvieron | repitieron | vistieron |
El camarero nos sirvió las cañas en menos de un minuto.
The waiter served us the beers in under a minute.
Repitió el mismo chiste tres veces hasta que alguien se rio.
He repeated the same joke three times until someone laughed.
Se vistió en cinco minutos y salió corriendo.
She got dressed in five minutes and ran out.
Sentir, preferir, mentir, divertirse — the e→ie group flattens to -i-
These verbs are e→ie in the present (siento, prefiero, miento, me divierto), but they collapse to a simple -i- in the third-person preterite. The diphthong is dropped, not preserved.
| Subject | sentir | preferir | divertirse |
|---|---|---|---|
| yo | sentí | preferí | me divertí |
| tú | sentiste | preferiste | te divertiste |
| él / ella | sintió | prefirió | se divirtió |
| nosotros | sentimos | preferimos | nos divertimos |
| vosotros | sentisteis | preferisteis | os divertisteis |
| ellos / ellas | sintieron | prefirieron | se divirtieron |
Sintió un pinchazo en el costado y se sentó.
He felt a stitch in his side and sat down.
Prefirió quedarse en casa esa noche.
She preferred to stay home that night.
Los niños se divirtieron muchísimo en la fiesta.
The kids had a great time at the party.
No te mentí — te dije la verdad desde el principio.
I didn't lie to you — I told you the truth from the start.
This collapse from ie in the present to plain i in the third-person preterite often surprises learners. The mental model that helps: the -ió and -ieron endings already carry an -i-, and Spanish doesn't stack vowels here. So the stem reduces to the simplest form that still signals the change.
Reír and freír — a small accent twist
The verbs reír ("to laugh") and freír ("to fry") are e→i stem-changers with one extra wrinkle: in the third-person singular preterite, the stem r- + -ió contracts to a single syllable. Older norms wrote rió with accent; since the 2010 RAE spelling reform, the accent is no longer written — because rio is now treated as a monosyllable (the i-o counts as a diphthong, not a hiatus), and Spanish monosyllables do not take a tilde unless it is diacritical. The same applies to frio (from freír). Note that this does not extend to sonreír (or any other polysyllabic compound): sonrió keeps the accent because it is a three-syllable aguda ending in a vowel (son-ri-ó), and the regular accent rules require the tilde.
| Subject | reír | freír | sonreír |
|---|---|---|---|
| yo | reí | freí | sonreí |
| tú | reíste | freíste | sonreíste |
| él / ella | rio | frio | sonrió |
| nosotros | reímos | freímos | sonreímos |
| vosotros | reísteis | freísteis | sonreísteis |
| ellos / ellas | rieron | frieron | sonrieron |
In practice, you'll see rió and frió written all over the internet by native speakers — the older norm is deeply entrenched. Both rio and rió will be read aloud the same way. Style guides aligned with the RAE (El País, El Mundo, La Vanguardia) follow the post-2010 rule and write rio, frio. Strict prescriptive editing marks rió and frió as wrong since 2010 — but only for these monosyllables. Sonrió, sofrió (from sofreír), desleyó and similar polysyllables are unaffected by the reform: they kept the accent then, and they keep it now.
Se rio a carcajadas con el chiste.
He laughed his head off at the joke.
Frio las patatas en aceite de oliva.
She fried the potatoes in olive oil.
Sonrió tímidamente cuando le dimos el regalo.
She smiled shyly when we gave her the present.
Todos sonrieron cuando entró el bebé.
Everyone smiled when the baby came in.
Note also that the yo and tú forms — reí, reíste; freí, freíste — keep the accent on the í because there is a hiatus to mark there (re-í, two syllables, with the second one stressed).
Why only -ir verbs?
The reason this pattern is exclusive to -ir verbs is historical. In Latin, the third-conjugation (-ere) and fourth-conjugation (-ire) verbs had different vowel behavior in the perfect tense. Spanish inherited the -ir class from Latin's -ire, and the inherited vowel pattern includes this third-person i- shift. -ar verbs (from Latin -are) and -er verbs (from Latin -ere) never had this pattern.
The diagnostic, mentioned above, is to check the present indicative. If the verb stem-changes (e→i or e→ie) in the present, it carries the change into the third-person preterite. If the present is fully regular, the preterite is too. This rule is exceptionless among standard verbs.
A working list of e→i preterite verbs
| Verb | Meaning | él form | ellos form |
|---|---|---|---|
| pedir | to ask for | pidió | pidieron |
| servir | to serve | sirvió | sirvieron |
| repetir | to repeat | repitió | repitieron |
| seguir | to follow | siguió | siguieron |
| conseguir | to manage to | consiguió | consiguieron |
| perseguir | to pursue | persiguió | persiguieron |
| vestir(se) | to dress, get dressed | (se) vistió | (se) vistieron |
| despedir(se) | to say goodbye, dismiss | (se) despidió | (se) despidieron |
| medir | to measure | midió | midieron |
| elegir | to choose | eligió | eligieron |
| corregir | to correct | corrigió | corrigieron |
| impedir | to prevent | impidió | impidieron |
| sentir | to feel | sintió | sintieron |
| preferir | to prefer | prefirió | prefirieron |
| mentir | to lie | mintió | mintieron |
| divertir(se) | to amuse, have fun | (se) divirtió | (se) divirtieron |
| consentir | to consent | consintió | consintieron |
| arrepentirse | to regret | se arrepintió | se arrepintieron |
| reír(se) | to laugh | (se) rio | (se) rieron |
| freír | to fry | frio | frieron |
| sonreír | to smile | sonrió | sonrieron |
Note that dormir and morir follow a parallel pattern with o→u instead of e→i (durmió, durmieron; murió, murieron) — see stem change o→u in the preterite.
Why English speakers struggle here
The most common error is to overgeneralize the change to nosotros and vosotros. Learners who know that pidió and pidieron show pid- assume that pedimos and pedisteis should too — they sometimes write *pidimos. They don't. The change is genuinely confined to the third person.
A useful mnemonic: the stem change in the present is governed by the boot (yo, tú, él, ellos shift; nosotros, vosotros don't). The stem change in the preterite is governed by a much smaller subset — just él and ellos shift. Everyone else, including the yo form that does shift in the present, is regular in the preterite.
The second hurdle is the e→ie group. Learners who know prefiero often write *prefirió correctly but stumble on *prefirí (wrong — yo form is just preferí, no shift). The diphthong ie of the present doesn't carry into the preterite at all, neither in shifted nor in unshifted form. The stem flattens to prefer- in the regular slots and to prefir- in the third-person slots.
Common mistakes
❌ Nosotros pidimos lo mismo de siempre.
Wrong: the stem change doesn't apply to nosotros. The form is pedimos, with regular e.
✅ Nosotros pedimos lo mismo de siempre.
Correct: pedimos.
❌ Vosotros sirvisteis a los invitados con mucho cariño.
Wrong: vosotros keeps the regular stem. The form is servisteis.
✅ Vosotros servisteis a los invitados con mucho cariño.
Correct: servisteis.
❌ Mi hermano sentió raro al despertarse.
Wrong: sintió, not sentió — the third person stem changes to sint-.
✅ Mi hermano se sintió raro al despertarse.
Correct: se sintió. (Also note that sentir takes the reflexive when describing how one feels — sentirse.)
❌ Los niños divertieron mucho ayer.
Wrong: the third-plural form is divirtieron, with i, not e. Also needs the reflexive se.
✅ Los niños se divirtieron mucho ayer.
Correct: se divirtieron.
❌ Mi madre prefirió que yo me quedara, pero yo prefirí salir.
Wrong in the second clause: the yo form is preferí, with no stem change.
✅ Mi madre prefirió que yo me quedara, pero yo preferí salir.
Correct: preferí for yo, prefirió for él/ella.
❌ ¿Pedieron los niños postre?
Wrong: pidieron, with the stem shifted to pid-.
✅ ¿Pidieron los niños postre?
Correct: pidieron.
Key takeaways
- The e→i stem change in the preterite is exclusive to -ir verbs and applies only to the third-person singular and plural.
- The verbs in scope are exactly those that stem-change in the present indicative — either e→i (pedir, servir, repetir, seguir) or e→ie (sentir, preferir, mentir, divertirse).
- -ar and -er verbs are immune: comió, vivió, hablaron — no shift.
- Verbs that are e→ie in the present collapse to plain -i- in the preterite: sintió, not *sientió; prefirió, not *prefirió with ie.
- The yo, tú, nosotros, and vosotros forms are all regular: pedí, pediste, pedimos, pedisteis.
- Reír and freír in the third-person singular are rio, frio — no accent since the 2010 RAE reform (they are monosyllables). Sonreír is different: sonrió keeps the accent because it is a polysyllabic aguda.
- The parallel pattern with o→u appears in just two verbs (dormir → durmió, morir → murió) — see stem change o→u in the preterite.
- The same shift surfaces in the gerund (pidiendo, sintiendo, durmiendo) and the present subjunctive of these verbs.
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- Pretérito: cambio o>u en 3ª persona (dormir, morir)B1 — Only two verbs — dormir and morir — change o to u in the third-person preterite (durmió, murieron); every other form stays regular.
- Cambio vocálico: e>i (pedir, servir, repetir)A2 — The e→i stem change found only in certain -ir verbs: stressed e shifts to i in the boot forms — pido, sirvo, repito — while nosotros and vosotros keep the simple e.
- Cambio vocálico: e>ie (pensar, querer, preferir)A2 — The most common stem-change pattern in Spanish: stressed e becomes ie in the 'boot' forms — yo, tú, él, ellos — while nosotros and vosotros keep the simple e.
- pedirA1 — Full conjugation reference for pedir — an e→i stem-changing -ir verb (pido, pides, pide). Covers the third-person preterite (pidió, pidieron), the gerund (pidiendo), the present subjunctive (pida throughout), and the crucial pedir/preguntar distinction (request vs ask a question) that trips up English speakers.
- sentirA1 — Full conjugation reference for sentir (to feel, to sense, to regret) — an -ir stem-changer with two related changes (e>ie in stressed present forms, e>i in the preterite 3rd persons and the gerund). Includes every tense, the reflexive sentirse for emotional and physical states, and the contrast with the look-alike sentarse, which trips up nearly every learner.