what is it?
When narrating past events in Spanish, the imperfecto and the indefinido (pretérito indefinido / pretérito perfecto simple) divide the work between them. The imperfecto paints the background — ongoing states, habitual actions, or conditions that were already in progress — while the indefinido marks foregrounded events: actions that are complete, punctual, or that advance the plot. A third pattern, iba a + infinitivo, describes an intention that was in progress when something else cut it short. A fourth pattern, al + infinitivo, expresses «on doing X» or «when X happened» and is preferred over a finite clause when both clauses share the same subject.
when to use it
Background (imperfecto): Use the imperfecto for actions or states that were already ongoing when the main event occurred. These are the «stage-setting» details: weather, time, feelings, descriptions, or what someone was in the middle of doing.
Foregrounded event (indefinido): Use the indefinido for a specific, completed action that happens at a defined moment and moves the story forward. Each indefinido verb is a new «beat» in the narrative.
Interrupted intention (iba a + infinitivo): Use the imperfecto of ir + a + infinitivo to show that someone was about to do something. The interrupting event is always in the indefinido.
Simultaneous trigger (al + infinitivo): Use al + infinitivo when the same subject performs two actions and the second happens immediately upon the first. It is more concise than a cuando clause and is the preferred form in written and spoken B1+ Spanish.
formation
The three patterns each have a fixed structure. The conjugation table below shows the imperfecto forms of ir needed for the iba a pattern, followed by a summary of all three structures.
| subject | imperfecto of ir | example with a + inf. |
|---|---|---|
| yo | iba | iba a salir |
| tú | ibas | ibas a llamar |
| él / ella / usted | iba | iba a comer |
| nosotros/-as | íbamos | íbamos a salir |
| vosotros/-as | ibais | ibais a llamar |
| ellos / ellas / ustedes | iban | iban a llegar |
Background + event: [imperfecto] + cuando/y + [indefinido]
Interrupted intention: iba/ibas/… a + infinitivo + cuando + [indefinido]
Simultaneous trigger: al + infinitivo, + [main clause in indefinido or imperfecto]
The infinitivo in al + infinitivo never changes for person or tense. The subject is understood from context. Only use this construction when both clauses share the same subject.
examples in context
common pitfalls
Using the imperfecto for a punctual, plot-advancing event.
The imperfecto cannot mark a completed, one-off event that moves the story forward. «Me encontraba con Ana» implies a habitual or ongoing encounter, not a sudden meeting.
✗ Iba por la calle y me encontraba con Ana.
✓ Iba por la calle y me encontré con Ana.
Using the indefinido of ir a + infinitivo for an interrupted intention.
«Fui a salir» means «I went out (in order to leave)» — a completed action — not an intention that was cut short. The interrupted-intention pattern requires the imperfecto iba, which frames the intention as ongoing at the moment of interruption.
✗ Fui a salir cuando sonó el teléfono.
✓ Iba a salir cuando sonó el teléfono.
Using a finite cuando clause instead of al + infinitivo when the subjects match.
«Cuando llegué, lo vi» is grammatically correct, but when the subject of both verbs is the same, al + infinitivo is the more natural and idiomatic choice in Spanish. Defaulting to the finite clause can sound awkward or overly literal.
Less idiomatic: Cuando llegué a la oficina, vi que las luces estaban encendidas.
More idiomatic: Al llegar a la oficina, vi que las luces estaban encendidas.
Three sentences, graded here. Nothing is saved and no account is needed.
Mi hermana ___ llamar a mamá cuando se dio cuenta de que había perdido el móvil. (ir a)
Fill in the blank with the correct form of the verb in parentheses.