Past tenses

the preterite (the simple past for completed actions)

hablé (I spoke)

comí (I ate)

vivió (he/she lived)

hablaron (they / you-all spoke)

comimos (we ate)

fui (I was / I went — both verbs share this form)

hice (I did / I made)

tuve (I had)

estuve (I was / I stayed)

For completed past actions: a single finished event, a sequence of events, or an action at a specific time (ayer, de repente).

«habló» (with accent) is the preterite «he/she spoke»; «hablo» (no accent) is the present «I speak» — the tilde changes the meaning.

«-í» (comí, viví) — not the -ar ending «-é»; the -er and -ir families share the same preterite endings.

ser/ir → fui, hacer → hice, tener → tuve (also estar → estuve, decir → dije).

the imperfect (the past for habits, description and ongoing actions)

hablaba (I used to speak / I was speaking)

comía (I used to eat)

vivíamos (we used to live)

hablaban (they / you-all used to speak)

comías (you used to eat)

era (I was / it was)

iba (I used to go)

veía (I used to see)

hacía (it was — e.g. hacía frío, it was cold)

For past habits, descriptions and background, age/time/weather, and «was -ing» — actions that repeat, stretch or describe rather than finish once.

ser → era, ir → iba, ver → veía. Every other verb is regular.

Imperfect — «todos los días iba al colegio». Using the preterite «fui» would mean it happened just once.

The -er/-ir imperfect ending is always «-ía» with a tilde; dropping it («comia») leaves the wrong vowel sound and is a marked error.

completed events: what happened, a single action, a sequence

background: description, habits, what was going on

comí = I ate (once, finished — preterite); comía = I used to eat / I was eating (imperfect)

fui = I went (once — preterite); iba = I used to go / I was going (imperfect)

ayer, de repente, una vez, el lunes (single, dated, finished moment)

siempre, normalmente, todos los días, mientras (repetition or ongoing scene)

ongoing action (imperfect comía) + the single event that interrupts (preterite sonó)

imperfecto: «tenía ocho años» (I was eight) — never the preterite «tuve»

imperfecto: «hacía frío / llovía» (it was cold / it was raining) as background

imperfecto: «eran las tres» (it was three o'clock) — never «fueron las tres»

Ask: the action that happened (preterite) or the scene/background around it (imperfect)?

The preterite (single event) interrupts the imperfect (ongoing action): «Mientras leía, llamaron a la puerta.»

The imperfect: tenía ocho años, eran las tres, hacía frío — these describe the past scene.

Using the preterite for description/age/weather, and using the imperfect for a one-off completed event.

the present perfect (haber + past participle = «have/has done»)

he, has, ha, hemos, habéis, han

hablado (he hablado = I have spoken)

comido (he comido = I have eaten)

vivido (he vivido = I have lived)

hecho (he hecho = I have done/made)

dicho (he dicho = I have said)

visto (he visto = I have seen)

escrito (he escrito = I have written)

vuelto / puesto / abierto (he vuelto, he puesto, he abierto)

Conjugate haber (he/has/ha/hemos/habéis/han) for the person, then add the past participle (-ado / -ido).

For the recent past connected to now (hoy, esta semana), for ya / todavía no, and for life experience («¿Has estado alguna vez…?»).

No — after haber the participle never changes for gender or number: «he comido», never «he comida».

Agreeing the participle after haber, splitting haber + participle, or using a wrong irregular («escribido» instead of «escrito»).