English has one simple past tense and Spanish has two, which means every past-tense sentence you build forces a decision English never asked you to make. The decision is not about when something happened - both tenses describe the past - but about how you are framing it.
The usual shorthand is completed versus ongoing, and it is a reasonable start that falls apart on sentences like viví en México cinco años, where something lasted half a decade and still takes the preterite. A better frame: the preterite reports an event, and the imperfect describes a situation. The preterite moves a story forward one step. The imperfect fills in the backdrop against which those steps happen.
This guide covers the forms of both tenses, the jobs each one does, the small set of verbs whose English translation changes depending on which you pick, and how the two work together when you actually tell someone what happened.
The forms
The imperfect is the easier of the two and one of the most regular tenses in Spanish. For -ar verbs the endings are -aba, -abas, -aba, -ábamos, -aban: hablaba, hablabas, hablaba, hablábamos, hablaban. For -er and -ir verbs they are -ía, -ías, -ía, -íamos, -ían: comía, vivía, and so on. Every -ía form carries a written accent.
Only three verbs are irregular in the imperfect in the entire language: ir gives iba, ser gives era, and ver gives veía. Learn those three and the imperfect is finished.
The preterite is where the work is. Regular -ar verbs take -é, -aste, -ó, -amos, -aron: hablé, hablaste, habló, hablamos, hablaron. Regular -er and -ir verbs take -í, -iste, -ió, -imos, -ieron: comí, comiste, comió, comimos, comieron. The accents on the yo and third-person forms are not decorative - habló and hablo are different tenses and different people.
One overlap catches everyone: for -ar and -ir verbs the nosotros preterite is identical to the present. Hablamos and vivimos can mean we speak or we spoke, and only context tells you which. Spanish tolerates this because context almost always does the job.
The frequent irregular preterites are unpredictable and must be memorised. Ser and ir share the same forms - fui, fuiste, fue, fuimos, fueron - so fui can mean I was or I went. Tener gives tuve, hacer gives hice with hizo in the third person, decir gives dije and dijeron, estar gives estuve, and poder gives pude. Notice that these irregular stems carry no accents at all.
hablaba, hablabas, hablaba, hablábamos, hablaban
imperfect of hablar
The most regular tense in Spanish
era, iba, veía
ser, ir, ver in the imperfect
The only three irregular verbs in the whole tense
hablé, hablaste, habló, hablamos, hablaron
preterite of hablar
Accents on hablé and habló are load-bearing
fui, tuve, hice, dije, estuve, pude
ser/ir, tener, hacer, decir, estar, poder
Irregular preterite stems - no accents on these forms
What the preterite does
The preterite reports. It presents an event as a complete package with a beginning and an end, viewed from outside. If you are telling someone what happened - the sequence of things that occurred - you are in the preterite.
This includes events that lasted a long time, which is where the completed-versus-ongoing rule misleads people. Viví en México cinco años is preterite because the five-year period is being presented as one finished block. Duration does not matter; boundedness does.
It also covers sudden events, single occurrences, and any action with a stated number of repetitions. Lo hice tres veces takes the preterite because three times is a closed count. And when one thing interrupts another, the interruption is preterite: it is the event, and whatever it interrupted is the backdrop.
De repente empezó a llover.
Suddenly it started to rain.
A single bounded event - the classic preterite
Ayer fui al mercado.
Yesterday I went to the market.
fui serves both ser and ir; here context makes it ir
Me di cuenta del error.
I realised the mistake.
A moment of realisation, not an ongoing state
Viví en México cinco años.
I lived in Mexico for five years.
Long, but presented as one closed block
What the imperfect does
The imperfect describes. It sets a scene without marking where it started or ended: what things were like, what was going on, what used to happen regularly. If you could naturally say used to or was doing in English, the imperfect is almost certainly right.
Its three main jobs are habits, ongoing background action, and description. Habits: siempre iba al mercado los sábados. Background: leía cuando sonó el teléfono - the reading was already underway when the phone cut in. Description: the weather, the time, ages, physical and emotional states, and anything that sets up a situation rather than advancing it.
Two specific cases are worth memorising because they are unavoidable and always imperfect. Telling the time in the past is always imperfect: eran las tres. And describing the weather as a backdrop is imperfect: hacía frío. Neither is an event; both are scenery.
Cuando era niño, vivía en México.
When I was a child, I lived in Mexico.
Both verbs describe a state, not an event
Siempre iba al mercado los sábados.
I always went to the market on Saturdays.
A habit - English used to go
Eran las tres.
It was three o'clock.
Time in the past is always imperfect
Hacía frío.
It was cold.
Weather as backdrop
The verbs whose meaning changes
A handful of very common verbs translate differently depending on the tense, because the preterite turns an ongoing state into the moment it started or the point at which it was acted on. These are not exceptions; they are the general rule applied to verbs that describe states.
Saber in the imperfect means knew: sabía la respuesta. In the preterite it means found out: lo supe ayer - the moment the knowledge arrived. Conocer in the imperfect means was acquainted with; in the preterite it means met for the first time: conocí a Ana en 2020.
Querer in the imperfect means wanted, with no information about what happened next. In the preterite it usually implies an attempt: quise ayudar suggests I tried. Negated in the preterite it implies refusal: no quiso venir means he refused to come, not merely that he did not want to.
Tener que follows the same logic. Tenía que salir means I was supposed to leave, and says nothing about whether I did. Tuve que salir means I had to leave and did. Poder behaves similarly: podía means was able to in general, while pude means managed to on that occasion.
The pattern is consistent enough to be predictive: with state verbs, the imperfect gives you the state and the preterite gives you the moment it changed.
Sabía la respuesta.
I knew the answer.
An ongoing state of knowledge
Lo supe ayer.
I found out yesterday.
The moment the knowledge arrived
Conocí a Ana en 2020.
I met Ana in 2020.
First encounter - a bounded event
Tenía que salir.
I was supposed to leave.
Obligation as backdrop; whether I left is unstated
Tuve que salir.
I had to leave, and I did.
The obligation was acted on
How they work together in a story
The two tenses are not rivals to be chosen between sentence by sentence. Real narration uses both at once, and once you see the division of labour, most individual choices answer themselves.
Think of it as a stage. The imperfect builds the set: the time, the weather, who was there, what they were doing, how everyone felt. The preterite is what walks on stage and does something. A paragraph of narration typically opens with a run of imperfects to establish the situation, then switches to preterite for the events, then drops back to imperfect for reactions and descriptions.
The clearest single pattern is interruption, and it is worth drilling on its own: an ongoing imperfect action gets cut across by a preterite event. Leía cuando sonó el teléfono. Estaba cansado, por eso descansé - the tiredness is the situation, the rest is what I did about it. Same sentence, both tenses, each doing its own job.
A practical way to practise: take an anecdote you can already tell in the present and retell it in the past. Do it out loud, more than once, and pay attention to the places where you hesitate. Those hesitations are the specific verbs you need to work on, and they are usually the state verbs from the previous section rather than the regular endings.
Leía cuando sonó el teléfono.
I was reading when the phone rang.
Imperfect backdrop, preterite interruption
Estaba cansado, por eso descansé.
I was tired, so I rested.
State in the imperfect, action in the preterite
Eran las tres cuando llegó.
It was three o'clock when he arrived.
Time is always imperfect; the arrival is an event
Common mistakes and how to avoid them
The most common error is treating duration as the deciding factor. Learners reach for the imperfect whenever something lasted a while, which produces vivía en México cinco años where viví is wanted. Ask whether the period is being presented as a closed block, not how long it was.
The second is defaulting to the preterite for everything because it feels like the real past tense. This produces technically comprehensible narration with no texture - a list of events with no scene around them. If your past-tense speech feels flat, you are probably under-using the imperfect.
The third is dropping accents. Hablo, habló and hablaba are three different words, and the first two differ only by a mark. In typed practice, get the accents right from the beginning; retrofitting them later is much harder than learning them attached to the form.
The fourth is over-relying on trigger words. Ayer, siempre and mientras are useful hints, not rules - you can say siempre with a preterite when you mean a closed period. Learn the frame, not the keyword list.
- Length does not decide it; boundedness does.
- Under-using the imperfect makes narration flat.
- Accents distinguish hablo, habló and hablaba.
- Time markers are hints, not rules.
Frequently asked questions
- What is the quickest way to decide between them?
- Ask whether you are reporting an event or describing a situation. Events that move the story forward take the preterite; scenery, habits and ongoing states take the imperfect. Length is irrelevant - a five-year stay takes the preterite if you present it as one closed period.
- Why is viví en México cinco años not imperfect?
- Because the five years are being presented as a single completed block with a start and an end. The imperfect would describe what life was like during that time: vivía en México y trabajaba en una escuela.
- Which verbs change meaning between the two tenses?
- Mainly state verbs. Sabía means knew while supe means found out; conocía means was acquainted with while conocí means met; tenía que means was supposed to while tuve que means had to and did. The preterite marks the moment a state began or was acted on.
- Why do fui and fue serve two different verbs?
- Ser and ir share identical preterite forms - fui, fuiste, fue, fuimos, fueron. Context always disambiguates: fui al mercado is clearly ir, while fui estudiante is clearly ser.
- Do I really need the accents?
- Yes. Hablo is I speak, habló is he spoke, and hablaba is I or he used to speak. In the preterite the accent is the only thing separating present from past in the first and third person, so learn each form with its accent attached.
Now make it stick
Reading a rule once is not the same as recalling it mid-sentence. Fijario's flashcards, typed verb drills, and daily quiz turn what you just read into something automatic.