Section 19.5 — Stem-Changing -IR Verbs (e→i and o→u)
19.1 Regular Preterit Endings19.2 Uses of the Preterit19.3 Past Time Markers19.4 Spelling-Change Verbs19.5 Stem-Changing -IR Verbs19.6 Ser and Ir in the Preterit19.7 High-Frequency Irregular Preterit Verbs
Spanish Grammar — Stem-Changing -IR Verbs
Section 19.5 · e→i: pedir, servir, sentir, seguir · o→u: dormir, morir · usted & ustedes only · yo & nosotros stay regular
📖 Introduction — Section 19.5: Stem Changes in the Preterit
Section 19.4 showed spelling changes that affect only the yo form. Section 19.5 introduces a different kind of change: stem vowel changes that affect only the usted and ustedes forms. This is the mirror image — instead of yo being the irregular form, usted and ustedes carry the variation while yo and nosotros remain completely regular.
Only -IR verbs that already have a stem change in the present tense carry this pattern into the preterit. There are two changes: e→i (pedir: pidió, pidieron) and o→u (dormir: durmió, durmieron). The yo form is always regular: pedí, dormí. The nosotros form is always regular: pedimos, dormimos. This makes these verbs predictable once the pattern is learned — and they appear constantly in medical, caregiving, and professional settings.
e→i: pedir, servir, sentir, seguir, sugerir, repetiro→u: dormir, morirusted & ustedes onlyyo & nosotros: fully regular-IR verbs only — never -AR or -ERtú: always regular — pediste · dormiste · sentiste · original stem vowel
⚡ The Two Stem Changes — Usted & Ustedes Forms Only
e → i • -IR verbse → i
The stem vowel e shifts to i in the usted and ustedes preterit forms. Yo and nosotros keep the original e.
Yopedí✓ regular e
Ustedpidíó▲ e→i
Nosotrospedimos✓ regular e
Ustedespidieron▲ e→i
o → u • -IR verbso → u
The stem vowel o shifts to u in the usted and ustedes preterit forms. Yo and nosotros keep the original o.
Yodormí✓ regular o
Usteddurmió▲ o→u
Nosotrosdormimos✓ regular o
Ustedesdurmieron▲ o→u
The pattern is the mirror of Section 19.4: Spelling-change verbs were irregular in yo only. Stem-changing -IR verbs are irregular in usted and ustedes only. Yo and nosotros are always regular in both systems. Tú is also always regular: The tú preterit ending is -iste, which is not a third-person form. Tú pediste · tú dormiste · tú sentiste — all use the original stem vowel. Tú joins yo and nosotros as a regular subject for these verbs.
👤 Who Changes — Full Paradigm: PEDIR & DORMIR
Green = regular (original stem vowel) • Orange = stem change applied • Blue = tú (always regular)
PEDIR (e→i)
Yopedí✓ regular
Túpediste✓ regular
Ustedpidíó▲ e→i
Nosotrospedimos✓ regular
Ustedespidieron▲ e→i
DORMIR (o→u)
Yodormí✓ regular
Túdormiste✓ regular
Usteddurmió▲ o→u
Nosotrosdormimos✓ regular
Ustedesdurmieron▲ o→u
The two-subject rule — and why tú is always regular: Only usted and ustedes trigger the stem change. Yo, tú, and nosotros all use the original stem vowel with their regular preterit endings. When in doubt about a form, ask: is the subject usted or ustedes? If yes, apply the change. If no — whether the subject is yo, tú, or nosotros — keep the original vowel. Tú pediste · tú dormiste · tú sentiste: never *pidiste, *durmiste, *sintiste.
When an -IR verb has the stem vowel e and that verb carries a stem change in the present tense, the e shifts to i in the usted and ustedes preterit forms. The yo form stays regular: pedí, serví, sentí. The nosotros form stays regular: pedimos, servimos, sentimos. Only usted and ustedes show the change: pidíó, pidieron · sirvió, sirvieron · sintió, sintieron. In medical settings, these verbs are constant: ¿Usted pidíó una cita? (Did you request an appointment?) La paciente se sintió mejor. (The patient felt better.) Los enfermeros sirvieron el almuerzo. (The nurses served lunch.) Recognizing the e→i pattern in usted and ustedes forms is essential for reading and writing medical notes accurately.
Only -IR verbs with present-tense stem changes carry this into the preterit: Regular -IR verbs (like vivir, abrir, escribir) do not have stem changes and are fully regular in the preterit. The e→i preterit change only applies to -IR verbs that already show e→ie or e→i in the present tense. -AR and -ER verbs never carry stem changes into the preterit. Tú is always regular: The tú preterit uses -iste, which is not a third-person ending. Tú pediste · tú sentiste · tú serviste — all use the original e in the stem. Never *pidiste, *sintiste, or *sirviste for tú.
✏️ e→i verbs in medical and professional sentences:
¿Usted pidíó una cita con el médico especialista la semana pasada?
La paciente se sintió mejor después de tomar la medicina recetada.
Los enfermeros sirvieron el almuerzo a todos los pacientes a las doce.
El paciente repitió su nombre y fecha de nacimiento dos veces.
Ustedes prefirieron esperar en la sala de recepción hasta la cita.
2. The o→u Change — Dormir and Morir
durmió / durmieron · murió / murieron — only two verbs
The o→u stem change in the preterit applies to exactly two verbs: dormir (to sleep) and morir (to die). Both follow the same pattern: yo and nosotros keep the original o — dormí, dormimos, morí, morimos — while usted and ustedes show the u: durmió, durmieron, murió, murieron. Dormir is among the highest-frequency verbs in medical and caregiving settings: ¿Usted durmió bien anoche? is a standard patient-intake question in nearly every clinical encounter. Los niños durmieron por ocho horas is the kind of sentence used constantly in pediatric and caregiving reports. Morir appears in clinical documentation and incident reports: El paciente murió en la ambulancia (The patient died in the ambulance).
Memorizing dormir and morir together: Because only two verbs carry the o→u change, it is worth memorizing them as a pair. Both shift the stem o to u in usted and ustedes: durmió/durmieron and murió/murieron. No other -IR verb carries o→u into the preterit. Tú is always regular for dormir and morir too:Tú dormiste (original o, no change). Tú moriste (original o, no change). The tú ending -iste is not a third-person form, so the o→u change never applies. Dormiste (not *durmiste) and moriste (not *muriste) for tú.
✏️ Dormir and morir in medical and caregiving sentences:
¿Usted durmió bien anoche o tuvo dificultad para descansar?
Los niños durmieron por ocho horas sin interrupciones esta noche.
El paciente murió en la ambulancia antes de llegar al hospital.
Ustedes durmieron juntos en la sala de espera mientras esperaban.
Yo dormí muy poco anoche — la misma situación que el paciente reportó.
The stem change in the preterit of these -IR verbs follows the same pattern as their present-tense counterparts: only the third person (usted, ustedes) triggers the change. Yo, tú, and nosotros are entirely predictable — they use the original stem vowel with the regular preterit endings. Yo pedí (regular, original e). Tú pediste (regular, original e). Nosotros pedimos (regular, original e). Yo dormí (regular, original o). Tú dormiste (regular, original o). Nosotros dormimos (regular, original o). This means that if you are reporting your own actions (yo), actions directed at someone informal (tú), or collective actions (nosotros), you never need to apply the stem change.
Practical value for professional communication: When writing in the first person (yo) or addressing someone informally (tú), all -IR verbs including stem-changers are regular: Yo pedí los registros · Tú pediste los registros · Yo sentí el problema · Tú sentiste el cambio · Nosotros pedimos la información. The stem change only requires attention when writing about what usted or ustedes did. Three subjects are always safe: yo, tú, and nosotros.
✏️ Yo and nosotros forms staying regular — contrast with usted:
Yo pedí los registros — usted pidíó los mismos registros ayer.
Yo dormí bien — pero el paciente no durmió nada anoche.
Nosotros servimos el desayuno — los voluntarios sirvieron el almuerzo.
Yo sentí el cambio de temperatura — el paciente lo sintió también.
Nosotros seguimos el protocolo — el equipo siguió el mismo procedimiento.
4. Medical Settings — High-Frequency Clinical Sentences
¿durmió bien? · ¿pidíó algo? · se sintió mejor · siguió las instrucciones
In clinical and caregiving environments, stem-changing -IR verbs appear in the most common intake questions and status reports. The question ¿Usted durmió bien anoche? is asked at nearly every patient encounter. ¿Le pidíó algo el doctor? (Did the doctor ask you for something?) checks compliance. La paciente se sintió mejor después de la medicina (The patient felt better after the medication) is a standard progress note form. Ellos prefirieron esperar en la recepción (They preferred to wait in reception) handles patient choices. El paciente siguió las instrucciones del alta (The patient followed the discharge instructions) documents compliance. These six sentence types — sleep assessment, request check, symptom improvement, preference, compliance, service — cover the vast majority of clinical preterit usage for these verbs.
Sentir vs. sentirse:Sentir used alone means “to feel (something)” with a direct object: sintió dolor (felt pain). Sentirse is reflexive and means “to feel (a condition)”: se sintió mejor (felt better). Both follow the same e→i stem change in usted and ustedes. In medical notes, you will see both: El paciente sintió náuseas (felt nausea) and El paciente se sintió mareado (felt dizzy).
✏️ Clinical intake questions and status reports:
¿Usted durmió bien anoche o tuvo problemas para dormir?
¿Le pidíó algo el doctor durante la consulta de ayer?
La paciente se sintió mejor después de recibir la medicina intravenosa.
Ellos prefirieron esperar en la recepción en lugar de la sala general.
El paciente siguió todas las instrucciones del alta sin problema.
5. Putting It Together — All Four Forms in Context
The complete picture: stem-changing -IR verbs have two forms in the preterit — the regular form (yo, nosotros) and the stem-change form (usted, ustedes). Practising all four subjects together in the same sentence or paragraph locks the complete paradigm into memory. Yo pedí información · Usted pidíó información · Nosotros pedimos información · Ustedes pidieron información. The sentence structure is identical; only the subject and the stem vowel change. In professional contexts, you will need to shift between subjects constantly — reporting your own actions (yo/nosotros, always regular) and reporting patient or colleague actions (usted/ustedes, stem change applies). Drilling all four forms together builds the automatic subject-to-form connection that fluency requires.
Summary of the full -IR stem-change preterit system: (1) Only -IR verbs with present-tense stem changes carry the pattern into the preterit. (2) Two changes: e→i (pedir, servir, sentir, seguir, repetir, sugerir, mentir, preferir) and o→u (dormir, morir only). (3) Usted and ustedes: apply the change. (4) Yo, tú, and nosotros: always regular, original stem vowel. Tú forms: pediste · dormiste · sentiste · serviste · seguiste — all with original stem vowel, all regular. (5) All preterit endings remain standard — the only thing that changes is the stem vowel in the usted/ustedes forms.
✏️ All four forms in professional workplace and medical sentences:
Yo pedí el turno — usted pidíó el mismo turno — nosotros pedimos una solución.
Yo dormí seis horas — usted durmió ocho — los pacientes durmieron poco.
Nosotros servimos el desayuno temprano; el personal de noche sirvió la cena.
El doctor sugirió reposo — el paciente lo siguió y se sintió mejor.
Ustedes pidieron los registros — nosotros los pedimos también hace dos días.
📌 Key Rules — Stem-Changing -IR Verbs at a Glance
Who is affected: Only -IR verbs that already have a stem change in the present tense. -AR and -ER verbs never carry stem changes into the preterit.
Two changes: e→i (pedir, servir, sentir, seguir, sugerir, repetir, mentir, preferir) and o→u (dormir and morir — only two verbs).
Which subjects change: Usted and ustedes only — the third-person forms. They carry the stem change just as in the present tense.
Which subjects stay regular: Yo, tú, and nosotros always use the original stem vowel. Tú forms: pediste · dormiste · sentiste · serviste · seguiste. The tú ending -iste is not third-person, so no stem change ever applies.
The subject test: Is the subject usted or ustedes? Yes → apply the stem change. Is the subject yo, tú, or nosotros? → use the original vowel and regular ending. Three safe subjects, two changing subjects.
o→u is only two verbs: Dormir (durmió/durmieron; tú: dormiste) and morir (murió/murieron; tú: moriste). Memorize them as a pair.
Clinical priority: ¿Durmió bien? / ¿Tú dormiste bien? · Se sintió mejor / Tú te sentiste mejor · Pidíó algo / Tú pediste algo · Siguió las instrucciones / Tú seguiste las instrucciones. Both registers in clinical use.
Shadow & Speak — Section 19.5-A
Listen to each sentence, then repeat aloud during the countdown.
Sentences 1–8 drill the e→i usted and ustedes forms across the highest-frequency verbs in medical and professional contexts. Sentences 9–13 drill o→u (dormir and morir) in clinical settings. Sentences 14–19 drill the yo and nosotros regular forms in contrast with the usted/ustedes stem-change forms. Sentences 20–25 drill full paradigm chains and mixed-subject professional narratives. Sentences 26–28 drill the tú regular forms to confirm they never change: pediste, dormiste, sentiste — always original stem vowel alongside the contrasting usted forms.
How to Shadow & Speak
Step 1 — Name the subject before speaking: Before each sentence, say the subject aloud: “usted — stem change,” “yo — regular,” “nosotros — regular.” This pre-production labeling makes the two-subject rule conscious and prevents automatic application of the change to all forms.
Step 2 — Stress the changed vowel: In the usted and ustedes forms, the stem vowel is the changed one. Stress it slightly when practising: pi-DI-ó, dur-MI-ó, sin-TI-ó. Hearing the changed vowel clearly anchors it phonologically.
Step 3 — Immediately produce the yo contrast: After each usted/ustedes sentence, immediately say the yo form of the same verb: pidíó → pedí · durmió → dormí · sintió → sentí. This side-by-side contrast is the fastest way to internalize which subjects change and which do not.
Study Tips
The clinical intake drill: Memorize these five questions and answers as complete units: (1) ¿Durmió bien anoche? — Sí, dormí bien. (2) ¿Le pidíó algo el doctor? — Sí, me pidió los resultados. (3) ¿Se sintió mejor? — Sí, me sentí mucho mejor. (4) ¿Siguió las instrucciones? — Sí, las seguí. (5) ¿Prefirió esperar? — Sí, preferí esperar. These five question-answer pairs cover the most frequent clinical uses of these verbs and demonstrate the usted/yo contrast in a natural dialogue format.
The two-subject card: On one index card, write: “USTED / USTEDES → STEM CHANGES • YO / NOSOTROS → REGULAR.” Keep this card visible during all writing practice with -IR stem-changing verbs until the rule is automatic. The card eliminates the most common error: applying the stem change to yo or nosotros.
Dormir and morir as a medical pair: These two o→u verbs are clinically important. Practise them together in a four-form chain out loud: dormí · durmió · dormimos · durmieron then morí · murió · morimos · murieron. Two minutes of this chain drill locks both paradigms permanently.
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Quiz — Section 19.5-B
Choose the correct answer. 20 questions drawn randomly from a pool of 30.