Question

Explain the difference between the preterite and the imperfect.

Answer 1

Short answer: use the imperfect for background, habitual or ongoing past actions; use the preterite for completed actions that advance the story or happened at a specific time.

More detail

Preterite (pretérito indefinido)
- Use for actions viewed as finished, completed, or bounded in time.
- Use for actions that happened once or a specific number of times, or at a specific moment.
- Use for a series of completed actions that move the story forward.
- Signal words: ayer, anteayer, anoche, el año pasado, entonces, de repente.

Examples:
- Ayer compré un libro. (I bought a book yesterday — completed action)
- Llegó, vio y venció. (He arrived, saw, and conquered — sequence of completed events)

Imperfect (pretérito imperfecto)
- Use for habitual or repeated past actions (what used to happen).
- Use for setting the scene or giving background (time, age, weather, physical/mental states, descriptions).
- Use for ongoing actions in the past (often translated as "was/were ...-ing") or actions that were in progress when something else interrupted.
- Signal words: siempre, a menudo, normalmente, mientras, cada día, muchas veces.

Examples:
- Cuando era niño, jugaba al fútbol todos los días. (When I was a child, I used to/play soccer every day — habitual/background)
- Llovía cuando salí de casa. (It was raining when I left home — ongoing action interrupted by another)

Common contrasts / tricky verbs
- Interruption: Estaba leyendo cuando sonó el teléfono. (I was reading — imperfect — when the phone rang — preterite.)
- Querer: Quería verte = I wanted to see you (ongoing desire). Quise verte = I tried to see you / I made an attempt (or sometimes: I decided to see you).
- Haber: Había mucha gente = there were a lot of people (background). Hubo un accidente = there was an accident (an event).

Quick conjugation reminders (regular verbs)
- -ar: imperfect -aba, preterite -é (yo). Example: hablar → hablaba / hablé.
- -er/-ir: imperfect -ía, preterite -í (yo). Example: comer → comía / comí; vivir → vivía / viví.

Memory tip
- Imperfect = background, description, habitual (the scene). Preterite = plot, completed actions, specific events.

If you want, I can give more example pairs (same sentence with each tense) or practice exercises.