Chapter 19 · The Completed Past
Section 19.1 — Regular Preterit Endings for -ar, -er, and -ir
19.1 Regular Preterit Endings 19.2 Uses of the Preterit: Completed Actions 19.3 Past Time Markers 19.4 Spelling-Change Verbs in the Preterit 19.5 Stem-Changing -IR Verbs in the Preterit 19.6 Ser and Ir in the Preterit 19.7 High-Frequency Irregular Preterit Verbs

Spanish Grammar — Regular Preterit Endings

Section 19.1  ·  -AR verbs: -é / -aste / -ó / -amos / -aron · -ER/-IR verbs: -í / -iste / -ió / -imos / -ieron · accent marks mandatory on yo and usted forms · nosotros form identical to present for -ar/-ir

📖 Introduction — Chapter 19: The Completed Past (Preterit)

Spanish has two main past tenses. Chapter 19 focuses on the preterit (pretérito indefinido) — the tense used to describe actions that started and ended at a specific moment in the past. In any professional or medical setting in the Americas, the preterit is essential: reporting a completed task, describing a prior appointment, explaining a past symptom, or narrating what happened. Llamé ayer. El doctor firmó el formulario. Nosotros abrimos la clínica a las ocho.

Section 19.1 establishes the foundation: the regular preterit endings for all three verb classes (-ar, -er, -ir) across the five key subjects (yo, tú, usted, nosotros, ustedes). Two critical features distinguish this tense: (1) mandatory written accents on the yo and usted forms without which meaning changes entirely, and (2) the nosotros form is identical to the present tense for -ar and -ir verbs — context resolves ambiguity. The tú forms (-aste / -iste) are distinct and unambiguous — no accent needed, no overlap with present tense.

-AR: -é / -aste / -ó / -amos / -aron -ER/-IR: -í / -iste / -ió / -imos / -ieron accents mandatory on yo & usted nosotros identical to present (-ar/-ir) -er/-ir share all endings tú: -aste (-AR) · -iste (-ER/-IR) · no accent needed

⚡ The Regular Preterit Conjugation System

-AR Verbs — Trabajar / Hablar / Llamar
Yo -é Trabajé I worked
Tú -aste Trabajaste You worked
Usted -ó Trabajó You worked
Nosotros -amos Trabajamos We worked
Ustedes -aron Trabajaron You all worked
-ER & -IR Verbs — Comer / Escribir (shared endings)
Yo -í Comí / Escribí I ate / wrote
Tú -iste Comiste / Escribiste You ate / wrote
Usted -ió Comió / Escribió You ate / wrote
Nosotros -imos Comimos / Escribimos We ate / wrote
Ustedes -ieron Comieron / Escribieron You all ate / wrote
Accent marks are mandatory and meaning-changing:  Hablo (I speak, present) vs. Habló (You/he spoke, preterit).  Trabajé = I worked  ·  Trabajó = You worked. Without the accent, the word means something different or belongs to a different tense entirely.
⭐  -ER and -IR verbs share every ending in the preterit:  comí = escribí · comió = escribió · comimos = escribimos · comieron = escribieron. Memorize one set, you have both.

́ Accent Marks — Mandatory and Meaning-Changing

▶ Present tense (no accent)

Hablo — I speak (right now)
Trabaja — You work (right now)
Ayuda — You help (right now)

▶ Preterit tense (accent required)

Habló — You/he spoke (past)
Trabajó — You/he worked (past)
Ayudó — You/he helped (past)

▶ First person present (no accent)

Firmo — I sign (present)
Compro — I buy (present)

▶ First person preterit (accent required)

Firmé — I signed (past)
Compré — I bought (past)

The accent is not optional:  In written Spanish, omitting the accent on firmé (writing firme instead) changes the form to the formal usted command — a completely different sentence with a completely different meaning. Similarly, trabajó without the accent would be misread as something else. In any professional document, the accent marks must appear on the yo (-é / -í) and usted (-ó / -ió) preterit forms.

👥 The Nosotros “Identical” Rule — Context Resolves Ambiguity

▶ Present tense — Nosotros

Hoy nosotros trabajamos.
Hoy nosotros escribimos.
Ahora abrimos la clínica.

▶ Preterit tense — Nosotros (same form!)

Ayer nosotros trabajamos.
Anoche nosotros escribimos.
El lunes abrimos la clínica.

How to tell which tense it is:  The time marker is everything. Hoy, ahora = present. Ayer, anoche, la semana pasada, el lunes = preterit. In professional speech, always include a time marker when using nosotros in the preterit to ensure clarity. Note: -ER nosotros (-imos) is also identical: comimos = we eat (present) or we ate (past). However, nosotros -ER/-ER forms are less commonly confused because the -imos ending is distinct from the present -emos (e.g., comemos present vs. comimos preterit — these are actually different).

🕐 Common Past Time Markers — Signal Words for the Preterit

AyerYesterday
AnocheLast night
La semana pasadaLast week
El mes pasadoLast month
Hace dos díasTwo days ago
Esta mañanaThis morning
Time markers are preterit triggers:  Whenever you use one of these words, the preterit tense almost always follows. They confirm that the action started and ended at a specific past moment. Covered in depth in Section 19.3.

📊 Vocabulary Chart: Regular Preterit Practice

InfinitiveYoTúUstedNosotrosUstedesAudio
Llamar — to call (-AR) Llamé Llamaste Llamó LlamamosLlamaron
Vender — to sell (-ER) Vendí Vendiste Vendió VendimosVendieron
Recibir — to receive (-IR) Recibí Recibiste Recibió RecibimosRecibieron
Cerrar — to close (-AR) Cerré Cerraste Cerró CerramosCerraron

1. -AR Verb Endings — -é / -ó / -amos / -aron

trabajé · firmó · caminamos · compraron · drop -ar, add ending to stem

To conjugate any regular -ar verb in the preterit: remove the -ar infinitive ending to get the stem, then add the ending. Hablar → habl-. Yo: habl + é = hablé. Tú: habl + aste = hablaste. Usted: habl + ó = habló. Nosotros: habl + amos = hablamos. Ustedes: habl + aron = hablaron. The accent marks on the yo (-é) and usted (-ó) forms are not optional. The tú form (-aste) carries no accent and is completely unambiguous — hablaste can only be the preterit tú form. Every -ar verb in regular preterit follows this exact pattern.

Building any -AR preterit form in three steps: (1) Write the infinitive. (2) Drop -ar to get the stem. (3) Add the ending: é / aste / ó / amos / aron. Llam-ar: yo llam-é · tú llam-aste · usted llam-ó · nosotros llam-amos · ustedes llam-aron. The tú ending -aste is unique to preterit — unlike yo/usted forms, it requires no accent and has no present-tense look-alike.
✏️ -AR preterit in professional context:
  1. Yo hablé con el cliente ayer por teléfono.
  2. Tú llamaste a la clínica esta mañana.
  3. Usted firmó el contrato esta mañana en la oficina.
  4. Nosotros caminamos al hospital el lunes pasado.
  5. Ustedes compraron la medicina en la farmacia ayer.

2. -ER and -IR Verb Endings — -í / -ió / -imos / -ieron

comí · escribió · abrimos · salieron · -er and -ir share all endings

For -er and -ir verbs, remove the infinitive ending to get the stem, then add the shared ending set. Comer → com-. Yo: com + í = comí. Tú: com + iste = comiste. Usted: com + ió = comió. Nosotros: com + imos = comimos. Ustedes: com + ieron = comieron. Identical for -ir: Escribir → escrib-. Yo: escribí. Tú: escribiste. Usted: escribió. Nosotros: escribimos. Ustedes: escribieron. The tú form (-iste) has no accent and is unambiguous — comiste can only mean “you ate” (preterit).

-ER nosotros in preterit vs. present are NOT identical: Unlike -ar/-ir, the -er nosotros forms differ: com-emos (present: we eat) vs. com-imos (preterit: we ate).  Tú preterit advantage: The -aste and -iste endings are completely unique to the preterit — no other tense uses them. Unlike yo and usted forms that need accent marks to distinguish tenses, tú preterit forms are always unambiguous.
✏️ -ER and -IR preterit in professional and medical context:
  1. Yo comí en la cafetería de la oficina al mediodía.
  2. Tú escribiste el reporte anoche antes de salir.
  3. Usted escribió el reporte anoche antes de salir.
  4. Nosotros abrimos la clínica a las ocho de la mañana el lunes.
  5. Ustedes salieron temprano de la clínica la semana pasada.

3. Accent Marks — The Distinction Between Tenses

firmé vs. firme · habló vs. habla · ayudé vs. ayuda · accent is grammatically required

The accent marks in the preterit are not decorative — they are grammatically required and change meaning completely when omitted. The yo form without accent (firmo) is present tense. The yo form with accent (firmé) is preterit. The usted form without accent (habla) is present tense. With accent (habló) is preterit. Most critically: the yo preterit form for -ar verbs (firmé) looks identical to the formal command for -er verbs (firme = sign!) if you drop the accent — leading to sentences that say the opposite of what was intended. In professional writing, documents, and medical records, these accent marks must always appear.

The accent that separates past from command: Firmé el contrato = I signed the contract. Firme el contrato = Sign the contract! The single accent mark is the difference between a statement and a command. For the usted form: Habló = You spoke / he/she spoke. Habla = You speak (present tense).  Tú preterit forms have no accent issue: Hablaste, firmaste, comiste, escribiste are 100% unambiguous — they are preterit only, with no present-tense or command look-alikes. The -aste/-iste endings belong exclusively to the preterit.
✏️ Accent contrast — present vs. preterit pairs:
  1. Hablé con el médico ayer. (I spoke — preterit)
  2. Hablo con el médico ahora. (I speak — present)
  3. Firmó el documento esta tarde. (You/he signed — preterit)
  4. Firma el documento cada semana. (You sign — present)
  5. Ayudé a la paciente con las instrucciones. (I helped — preterit)

4. The Nosotros Identical Form — Resolved by Context

trabajamos (today) = trabajamos (yesterday) · abrimos now = abrimos last week · time marker is the key

For -ar and -ir verbs, the nosotros preterit form is spelled and pronounced identically to the present tense form: trabajamos = trabajamos · abrimos = abrimos · caminamos = caminamos · escribimos = escribimos. This does not cause confusion in practice because Spanish speakers always use time markers (ayer, anoche, hoy, la semana pasada) to anchor the sentence in time. The time marker is the signal, not the verb form. Hoy trabajamos (present). Ayer trabajamos (preterit). A sentence with the nosotros form and no time marker relies entirely on discourse context — but in professional and medical speech, a time marker is always present and always resolves the ambiguity instantly.

-ER nosotros DOES change: Important exception — nosotros for -er verbs in the preterit is NOT the same as the present: comemos (we eat, present) vs. comimos (we ate, preterit). Vendemos (we sell) vs. vendimos (we sold). Only -ar and -ir nosotros forms are identical across tenses; -er nosotros is always distinct.  Tú has no ambiguity issue: Unlike nosotros, the tú preterit forms (-aste / -iste) are completely unique to the preterit. Trabajaste is always preterit; escribiste is always preterit. There is no tú present-tense form that looks like these endings.
✏️ Nosotros with time markers — distinguishing present from preterit:
  1. Hoy nosotros trabajamos en la clínica hasta las seis. (present)
  2. Ayer nosotros trabajamos diez horas sin descanso. (preterit)
  3. El lunes nosotros abrimos la oficina a las ocho en punto. (preterit)
  4. Anoche nosotros escribimos el informe final del trimestre. (preterit)
  5. Ahora nosotros abrimos los expedientes nuevos. (present)

5. Preterit in Professional and Medical Reporting

llamé ayer · firmó esta mañana · recibieron la semana pasada · real-world application

The preterit is the primary tense for professional and medical reporting in the Americas. When documenting what happened, recounting completed events, or describing a patient’s history, virtually every verb is in the preterit. El paciente llamó ayer (The patient called yesterday). Tú entregaste el formulario esta mañana (You turned in the form this morning — tú, -aste). Yo entregué el formulario esta mañana (I turned in the form — yo, -é). Ustedes recibieron el diagnóstico la semana pasada (You received the diagnosis last week). Nosotros cerramos la sala de urgencias a las diez (We closed the emergency room at ten). Every regular preterit sentence follows the same pattern: stem + appropriate ending + time marker for clarity.

Coming in Chapter 19: Section 19.1 covers only regular verbs with unchanged stems. Sections 19.4–19.7 introduce verbs that change spelling (buscar/busqué), verbs where the stem vowel shifts in certain forms (pedir/pidió), the high-frequency irregular pair ser/ir (both become fui/fue/fuimos/fueron), and other essential irregular preterit verbs (tener/tuve, hacer/hice, estar/estuve). The tú forms of these irregular verbs will also follow predictable patterns: fuiste, tuviste, hiciste, estuviste — all ending in -iste.
✏️ Regular preterit in real professional reporting:
  1. El paciente llamó ayer para cancelar su cita del jueves.
  2. Tú entregaste todos los formularios esta mañana.
  3. Ustedes recibieron el diagnóstico completo la semana pasada.
  4. Nosotros cerramos la sala de urgencias a las diez de la noche.
  5. Usted vendió los suministros que sobraron el mes pasado.

📌 Key Rules — Regular Preterit at a Glance

Shadow & Speak — Section 19.1-A

Listen to each preterit sentence, then repeat aloud during the countdown.

Sentences 1–5 drill -AR verbs across all five subjects (yo/tú/usted/nosotros/ustedes) in realistic professional contexts to establish the full ending pattern including -aste. Sentences 6–10 drill -ER verbs with the shared endings including tú -iste. Sentences 11–15 drill -IR verbs to build the parallel with -ER. Sentences 16–20 present minimal pairs (present vs. preterit) with accent contrast. Sentences 21–25 drill full professional reporting sentences. Sentences 26–28 focus specifically on the tú forms (-aste/-iste) to build automatic recall of the unaccented preterit tú ending.

How to Shadow & Speak

Step 1 — Name the ending before speaking: Before each sentence, say aloud the ending of the preterit verb: “é,” “ó,” “amos,” or “aron.” This keeps the paradigm visible and prevents defaulting to present-tense forms.

Step 2 — Stress the accented syllable: For yo and usted forms, give the final syllable a strong, clear stress: habl-É · habl-Ó · com-Í · comi-Ó. In the preterit, the stress is always on the ending — the opposite of how most present-tense forms are stressed.

Step 3 — Produce all four forms: After each sentence, immediately produce the same verb in all four preterit subjects as a chain: trabajé · trabajó · trabajamos · trabajaron. This chain drill is the fastest path to automatic preterit conjugation.

Study Tips

The two-column paradigm drill: On paper, write -AR endings in the left column and -ER/-IR endings in the right: é / í · ó / ió · amos / imos · aron / ieron. The contrast between the columns is the entire preterit for regular verbs. Drill this contrast until switching between columns by subject is automatic.

The accent-placement check: After every preterit sentence you write, go back and verify: (1) Does the yo form have an accent? (2) Does the usted form have an accent? If either answer is no and the verb is regular, add it. Build the habit of the two-form accent check before any sentence is considered complete.

Time marker + verb pairing: Choose five time markers (ayer, anoche, la semana pasada, esta mañana, hace dos días) and for each produce one -ar sentence, one -er sentence, and one -ir sentence. Fifteen sentences total. This exercise forces the automatic pairing of time marker → preterit that professional speech requires.

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Quiz — Section 19.1-B

Choose the correct answer. 20 questions drawn randomly from a pool of 30.

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