Cuando era niña, vivía en Barcelona. Un día, mis padres decidieron mudarse a Madrid.When I was a girl, I lived in Barcelona. One day, my parents decided to move to Madrid.

Both the preterite and the imperfect talk about the past, but they answer different questions: the preterite says what happened, and the imperfect says what things were like or what used to happen. Most of the time, choosing between them comes down to which of those two questions your sentence is actually answering.

Quick shortcut: reporting a completed event → preterite. Describing a background situation, a habit, or an ongoing state → imperfect.

The basic contrast

Preterite Imperfect
Answers What happened? What was going on? What was it like?
Presents the action as A completed whole Ongoing, in progress, or habitual
Typical cue words ayer, de repente, una vez, el año pasado, anoche todos los días, siempre, mientras, de niño/a, a menudo
Example Ayer llovió. (It rained yesterday — reporting the fact.) Llovía mucho ese verano. (It used to rain a lot that summer — a background pattern.)

These cue words are useful hints, not strict rules — the same word can sometimes appear with either tense depending on what the sentence is actually doing. Ayer llovió reports yesterday's rain as a fact; ayer, mientras trabajaba, llovía uses the imperfect for the same day because it's now describing the backdrop to something else.

The interrupted-action pattern

A very common structure pairs both tenses in one sentence: the imperfect sets the ongoing scene, and the preterite reports the single event that broke into it.

Mientras dormía, sonó el teléfono. (While I was sleeping, the phone rang.) Caminábamos por el parque cuando empezó a llover. (We were walking through the park when it started to rain.) Yo veía la televisión cuando llegaron mis amigos. (I was watching television when my friends arrived.)

In each case, the imperfect verb describes what was already in progress, and the preterite verb is the thing that happened at a specific moment within that backdrop.

Verbs that change meaning depending on the tense

A handful of common verbs are usually translated differently in English depending on which past tense they take, because the preterite frames them as the start or completion of something, while the imperfect describes an ongoing state:

Verb Imperfect Preterite
saber sabía — knew (a fact, ongoing) supe — found out
conocer conocía — knew (a person, was acquainted with) conocí — met (for the first time)
querer quería — wanted (ongoing desire) quise — wanted, and (with an infinitive whose result didn't follow) tried; no quise — refused
poder podía — was able to (in general) pude — managed to (in an affirmative, completed context); no pude — was unable to
tener tenía — had (ongoing possession/state) tuve — had, for a bounded period (tuve un coche dos años); also tuve que..., had to

Ya conocía a Marta, pero conocí a su hermano en la fiesta. (I already knew Marta, but I met her brother at the party.) No sabía la respuesta, pero al final la supe. (I didn't know the answer, but I eventually found it out.) These aren't automatic one-word translations — the infinitive and the surrounding context still shape the exact meaning.

Common mistakes

  • To simply report that you went to the cinema yesterday: ✅ Ayer yo fui al cine., not ❌ Ayer yo iba al cine. (iba al cine instead means "I was going/on my way to the cinema," normally continuing with something like cuando me encontré con Ana)
  • ❌ Cuando era niño, fui a la playa todos los veranos. → ✅ Cuando era niño, iba a la playa todos los veranos. (a repeated childhood habit needs the imperfect; the preterite would instead report a single trip)
  • ❌ Mientras yo comí, mi hermano llamó. → ✅ Mientras yo comía, mi hermano llamó. (here the imperfect is needed because comer is the action in progress when the call interrupts it — not because mientras itself always forces the imperfect; a mientras clause framing its own action as bounded can take the preterite too, e.g. Mientras estuve en Madrid, trabajé mucho)
  • ❌ La conocí muy bien. (meaning "I knew her well," ongoing) → ✅ La conocía muy bien. (an ongoing acquaintance needs the imperfect; the preterite conocí would instead mean "I met her")

Quick check

Choose the preterite or the imperfect form of the verb in parentheses.

  1. De pequeño, yo ___ (jugar) al fútbol todos los sábados.
  2. Anoche, nosotros ___ (cenar) en un restaurante nuevo.
  3. Ella ___ (dormir) cuando sonó la alarma.
  4. Yo no ___ (saber) la verdad hasta ayer.
  5. Mis abuelos ___ (vivir) en un pueblo pequeño cuando eran jóvenes.
Show answers
  1. De pequeño, yo jugaba al fútbol todos los sábados.   2. Anoche, nosotros cenamos en un restaurante nuevo.   3. Ella dormía cuando sonó la alarma.   4. Yo no supe la verdad hasta ayer.   5. Mis abuelos vivían en un pueblo pequeño cuando eran jóvenes.

Key takeaways

  • The preterite reports a completed event (what happened); the imperfect describes background, habits or ongoing states (what things were like).
  • Cue words like ayer or todos los días are helpful hints, not strict rules — the sentence's own meaning decides the tense.
  • The classic pattern pairs both: imperfect for the ongoing scene, preterite for the event that interrupted it.
  • A few verbs (saber, conocer, querer, poder, tener) shift meaning between the two tenses — the imperfect describes an ongoing state, the preterite marks its start or completion.
  • Getting comfortable with this contrast takes practice — it's normal to need to double-check which tense a sentence calls for, even at this level.