SER Conjugation: Master the Spanish "To Be" in Every Tense

Ser is the single most used verb in the Spanish language — and, naturally, the most irregular one too. Soy, fui, era, seré… at first glance the forms look like four different verbs. Here's the good news: you only need to master five or six forms per tense, and every one of them follows a pattern you can learn in minutes.

In this guide you'll find complete SER conjugation tables for every tense you'll actually use — present, preterite, imperfect, future, conditional and present subjunctive — with a real example sentence for every single form. No linguistics degree required. By the end, you'll take a five-question quiz to prove to yourself that the "impossible" verb isn't impossible at all.

The foundationWhat SER means (and when to use it)

Before drilling forms, lock in the job description. SER answers the question "what is it?" — it defines, identifies and classifies. You reach for ser whenever you're talking about:

• Identity — Soy Fernando. (I'm Fernando.)
• Origin — Somos de Canadá. (We're from Canada.)
• Profession — Mi madre es arquitecta. (My mother is an architect.)
• Characteristics — Eres muy paciente. (You're very patient.)
• Time & date — Son las dos. Hoy es jueves. (It's two o'clock. Today is Thursday.)

Spanish has a second "to be" — estar — for states, feelings and locations. If you're not sure when each one applies, read the full ser vs estar guide first; this article assumes you know why you're using ser and focuses on getting every form right, in every tense.

Tense nº 1SER in the present tense

The present tense of ser is wildly irregular — none of the six forms even starts with the letters s-e-r. But you already know more of it than you think: soy, eres, es appear in practically every Spanish sentence you've ever heard. In fact, es is one of the most frequent words in the entire language.

Six forms, thousands of sentences. Notice the s- pattern: soy, somos, sois, son.

A pattern worth spotting: four of the six forms begin with s- (soy, somos, sois, son). The two odd ones out — eres and es — pair naturally with tú and él/ella, and you'll hear them so often that they stick within days.

Tenses nº 2 & 3SER in the past: preterite vs imperfect

Spanish gives you two past tenses for ser, and they are not two flavors of the same thing. The preterite (fui, fue…) reports completed events and delivers verdicts. The imperfect (era, eran…) paints background scenery: descriptions, habits, ongoing states. Learn both tables, then learn the difference — that's where fluency lives.

SER — preterite conjugation

Heads up: these forms are 100% identical to the preterite of IR (to go). Context tells them apart.

SER — imperfect conjugation

Only one accent to remember in the whole table: éramos.

So when do you say fui and when do you say era? Use fui/fue for a completed event viewed as a whole — something that happened, ended, and can be summed up. Use era/eran for a background description or state — how things were while other stuff was going on. The same logic applies to every verb in the past; ser is just the verb you'll use it with most. For the full picture of when the preterite wins, see the Spanish preterite tense guide.

Tenses nº 4 & 5SER in the future and conditional

Here's your reward for surviving the past tenses: the future and conditional of ser are completely regular. Both are built on the full infinitive ser- plus the standard endings every Spanish verb uses — so if you know these twelve forms, you already know the pattern for the entire language.

Ser- + regular endings. The future says "will be"; the conditional says "would be."

Use the future for predictions and promises (will be), and the conditional for hypotheticals, polite suggestions and daydreams (would be). Spanish speakers also use the future to wonder out loud: ¿Quién será? — "I wonder who that is?"

Bonus tenseSER in the present subjunctive

You don't need to master the subjunctive on day one — but you will hear it constantly, because ser's subjunctive forms show up after some of the most common phrases in Spanish: espero que… (I hope that…), es importante que… (it's important that…), quiero que… (I want…). Whenever one of those triggers appears, ser switches to its se- forms:

One stem, six forms: sea, seas, sea, seamos, seáis, sean.

For now, just learn the two forms you'll use most — sea and seas — inside their trigger phrases. Say "Espero que sea…" and "Quiero que seas…" out loud a few times and the pattern installs itself.

PracticeQuiz: check yourself

Fill in the correct form of ser — then click each question to reveal the answer.

Common questionsFAQ: SER conjugation