Preterite vs Imperfect

The core distinction

Both are past tenses. The choice depends on how you frame the action, not when it happened.

	Preterite	Imperfect
Frame	completed, bounded event	ongoing, unbounded state or habit
Think of it as	a snapshot (one moment, done)	a video (background, continuous)
Translates roughly as	I did, she went, he said	I used to do, she was going, he would say

Same real-world event, different framing = different tense.

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Decision guide

Ask these questions:

Question	If yes →
Was it a one-time completed event?	Preterite
Did it happen a specific number of times?	Preterite
Was it a sequence of events (first… then…)?	Preterite
Did it interrupt an ongoing action?	Preterite
Was it a habit or repeated action?	Imperfect
Was it a background state or description?	Imperfect
Does it describe how things were (not what happened)?	Imperfect
Was it an ongoing action when something else occurred?	Imperfect

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Signal words

Preterite	Imperfect
ayer (yesterday)	siempre (always)
anoche (last night)	nunca (never)
la semana pasada (last week)	a veces (sometimes)
hace [X] años ([X] years ago)	todos los días (every day)
una vez (once)	de niño/a (as a child)
de repente (suddenly)	antes (before / used to)
entonces (then)	generalmente (generally)
por fin (finally)	mientras (while)
ese día (that day)	cada semana (every week)
al final (in the end)	cuando era joven (when I was young)

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Side-by-side: same sentence, both tenses

Preterite	Imperfect	Difference
Comí pizza. (I ate pizza — once, done)	Comía pizza todos los días. (I used to eat pizza every day)	single event vs habit
Fue al banco. (He went to the bank — that specific time)	Iba al banco los viernes. (He used to go to the bank on Fridays)	one event vs routine
Trabajé allí dos años. (I worked there for two years — period is over)	Trabajaba allí. (I worked/was working there — background state)	closed period vs ongoing state
Llamó a las 8. (She called at 8 — specific moment)	Llamaba siempre a las 8. (She always called at 8 — routine)	one-time vs habit
Vivieron en Madrid tres años. (They lived in Madrid for 3 years — over)	Vivían en Madrid. (They lived in Madrid — background description)	bounded period vs open state

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The classic combination: imperfect + preterite

A very common pattern: the imperfect sets the scene (background), and the preterite interrupts (specific event).

Imperfect (background)	Preterite (interruption)	English
Dormía	cuando sonó el teléfono.	I was sleeping when the phone rang.
Caminaba por el parque	cuando empezó a llover.	I was walking in the park when it started to rain.
Estudiaba	cuando llegó mi amigo.	I was studying when my friend arrived.
Leía un libro	cuando se fue la luz.	I was reading a book when the power went out.
Comíamos	cuando entró ella.	We were eating when she came in.
Hablaba por teléfono	cuando lo vi.	I was talking on the phone when I saw him.
Era de noche	cuando llegaron.	It was night when they arrived.
Llovía	cuando salí de casa.	It was raining when I left the house.
Tenía 10 años	cuando aprendí a leer.	I was 10 years old when I learned to read.
Trabajaba en Madrid	cuando conocí a mi esposa.	I was working in Madrid when I met my wife.

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Same verb, different tense, different meaning

Preterite	Imperfect	Meaning shift
(No) supe que llegaste.	(No) sabía que ibas a llegar.	I found out (moment of learning) vs I didn’t know (ongoing ignorance)
Quise llamarte.	Quería llamarte.	I tried to call you (and maybe did) vs I wanted to call you (unfulfilled)
Pude abrirlo.	Podía abrirlo.	I managed to open it (success) vs I was able to open it (ability existed)
Tuve que salir.	Tenía que salir.	I had to leave (and did) vs I was supposed to leave
Conocí a María.	Conocía a María.	I met María (first time) vs I knew María (ongoing relationship)

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Common mistakes

• ❌ Using preterite for descriptions of past state → ✅ “Era muy joven” (imperfect), not “Fue muy joven”
• ❌ Using imperfect for a specific completed event → ✅ “Ayer comí” (preterite), not “Ayer comía”
• ❌ Translating “I was + -ing” always as imperfect → ✅ sometimes a preterite interrupts: “Dormía cuando sonó el teléfono”
• ❌ Treating signal words as absolute rules → ✅ they’re strong hints, not guarantees; meaning drives the choice

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Summary

• Preterite = snapshot: completed, bounded, specific, sequential
• Imperfect = video: ongoing, habitual, descriptive, background
• Classic combo: imperfect (scene setting) + preterite (event that happened)
• Some verbs change meaning based on which tense is used (saber, conocer, poder, querer)

See also: Preterite — endings and examples.
See also: Imperfect — endings and examples.
See also: Present Perfect — the tense Castellano often prefers over preterite for today’s events.
See also: Past Tense Conjugation Table — all forms at a glance.