| A | B |
|---|
| changed past conditions, reactions | preterite |
| actions (single or consecutive) | preterite |
| habitual action limited in time | preterite |
| repeated actions | preterite |
| Actions--beginning and/or end | preterite |
| past conditions, beliefs | imperfect |
| habitual actions | imperfect |
| Actions--Middle, in progress, Interrupted | imperfect |
| projected actions (indirect discourse) | imperfect |
| no implication of change, reaction or action, or time limitation | imperfect |
| to indicate a sudden change, a reaction, or time limitation | preterite |
| to indicate objects that were present in the past | imperfect (i.e. había diez sillas en la clase) |
| to indicate events or actions that occur in the past | preterite (i.e hubo una tormenta) |
| he said that he was leaving in an hour | dije que salía en una hora |
| to know (something) | imperfect (sabía) |
| to fin our, to become informed, to realize | preterite (supo) |
| to know (someone) | imperfect (conocíamos) |
| to meet (for the first time, as in being introduced) | preterite (conocí) |
| to just have done something | imperfect (i.e. acabad de comer cuando llegaste) |
| to finish | preterite (i.e. acabé de comer y me fui) |
| to have an obligation, or to be due (not completed) | imperfect (debíamos cenar juntos/debía tener el bebé esa semana) |
| should (not) have, ought (not) to (contrary to reality) | preterite (debimos haber hablado de eso/no debiste haberme dich) |
| to be about to (not completed) | imperfect (íbamos a cenar juntos) |
| to go (completed action) | preterite (fuimos a trabajar) |
| to be able, can | imperfect (podían trabajar juntos) |
| to succeed, be able, manage, fail | preterite (no pudieron salir) |
| to want | imperfect (queríamos a viajar) |
| to attempt, to try, to refuse to | preterite (quiso escapar, pero nu pudo) |
| obligation (not necessarily fulfilled) | imperfect (tenía que trabajar, pero fui al cine) |
| fulfilled obligation | tuve que trabajar anoche |
