Basar Examples, Sentences & Quiz in Spanish

basar means “to base” in English, and this page shows you how it actually sounds in everyday Spanish — not just the conjugation table, but the verb in real sentences, in short dialogues, and in the mistakes learners make with it. Basar means to base, and it is the transitive verb for founding an opinion, a theory, a decision or a project on something: you base your opinion on the data, you base a theory on experience. It takes en for the foundation, as in basar mi opinión en los datos. Below you will find twelve example sentences grouped by tense, two short dialogues, the most common mistakes with corrections, and a ten-question quiz with explained answers. If you want the full tables first, start with the full conjugation of basar; if you want to study one tense in depth, see the basar present tense page.

basar in everyday use: examples with translations

In the present

Four sentences with basar in the present tense, for habits, facts and things happening right now.

  1. Yo baso mi opinión en los datos. — I base my opinion on the data.
  2. Él/Ella basa la teoría en la experiencia. — He bases the theory on experience.
  3. Nosotros/as basamos mi decisión en los hechos. — We base my decision on the facts.
  4. Ellos/as basan el proyecto en un estudio. — They base the project on a study.

In the past

Four sentences with basar in the past: the preterite for finished actions and the imperfect for habits and background.

  1. Ayer, Yo basé mi decisión en los hechos. — Yesterday, I based my decision on the facts.
  2. Antes, Nosotros/as basábamos el proyecto en un estudio. — Before, We used to base the project on a study.
  3. Ayer, Él/Ella basó mi opinión en los datos. — Yesterday, He based my opinion on the data.
  4. De niños, Ellos/as basaban la teoría en la experiencia. — As children, They used to base the theory on experience.

Plans, hopes and wishes

Four sentences with basar in the future, the conditional, the subjunctive and the present perfect — for plans, hypotheticals and things that have just happened.

  1. Mañana, Tú basarás mi opinión en los datos. — Tomorrow, You will base my opinion on the data.
  2. Yo basaría la teoría en la experiencia. — I would base the theory on experience.
  3. Espero que él base mi decisión en los hechos. — I hope he bases my decision on the facts.
  4. Él/Ella ha basado el proyecto en un estudio. — He has based the project on a study.

basar in context: two short dialogues

Making plans

Ana: ¿Tú basas mi opinión en los datos mañana? — Are you going to base my opinion on the data tomorrow? Luis: Sí, yo baso mi opinión en los datos todos los días. — Yes, I base my opinion on the data every day. Ana: ¿Y mañana basarás la teoría en la experiencia? — And tomorrow, will you base the theory on experience? Luis: Claro, mañana basaré la teoría en la experiencia sin falta. — Of course, tomorrow I will base the theory on experience without fail. Ana: Perfecto. Yo basaré mi decisión en los hechos también. — Perfect. I will base my decision on the facts too. Luis: Entonces quedamos mañana. ¡Hasta luego! — Then see you tomorrow. Bye!

Yesterday

Ana: ¿Qué hiciste ayer? — What did you do yesterday? Luis: Ayer basé mi decisión en los hechos. — Yesterday, I based my decision on the facts. Ana: ¿Y antes basabas el proyecto en un estudio? — And before, did you use to base the project on a study? Luis: Sí, antes basaba el proyecto en un estudio todos los días. — Yes, before, I used to base the project on a study every day. Ana: ¿Y tus hermanos basaron mi opinión en los datos? — And did your brothers based my opinion on the data? Luis: Sí, ellos basaron mi opinión en los datos por la tarde. — Yes, they based my opinion on the data in the afternoon.

Common mistakes

  1. Wrong: Yo basa mi opinión en los datos. — Right: Yo baso mi opinión en los datos. — The person matters: basa is the él/ella/Ud. form, while the yo form is baso. Using the third-person form with yo is one of the most common beginner errors.
  2. Wrong: Treating basar and basarse as identical in every context. — Right: Basar means to base, while basarse means to be based on something yourself. — They overlap, but each has uses the other does not: basar fits sentences such as Baso mi opinión en los datos, while basarse belongs in a different sentence. Check the meaning you want before choosing.
  3. Wrong: Yo soy basado la teoría en la experiencia. — Right: Yo he basado la teoría en la experiencia. — Spanish perfect tenses use haber, not ser: he basado, has basado, ha basado. Ser plus the participle makes a passive, not a perfect tense.
  4. Wrong: De niño, yo basé mi decisión en los hechos todos los días. — Right: De niño, yo basaba mi decisión en los hechos todos los días. — For a repeated habit in the past, use the imperfect (basaba), not the preterite. The preterite (basé) is for one finished action.

Quiz: test yourself

Ten questions on basar in use. Choose the right answer, then check the answer key below.

  1. Complete the sentence: Ellos/as ___ el proyecto en un estudio. (present tense) A. basan B. baso C. basas D. basa

  2. Complete the sentence: Ayer, Nosotros/as ___ mi opinión en los datos. (preterite tense) A. basé B. basaste C. basó D. basamos

  3. Complete the sentence: Antes, Tú ___ la teoría en la experiencia. (imperfect tense) A. basábamos B. basabais C. basabas D. basaba

  4. Complete the sentence: Mañana, Él/Ella ___ mi decisión en los hechos. (future tense) A. basaremos B. basará C. basaré D. basarás

  5. Complete the sentence: Nosotros/as ___ el proyecto en un estudio. (conditional tense) A. basaríamos B. basaría C. basarías D. basaríais

  6. Complete the sentence: Hoy, Yo ___ mi opinión en los datos. (present-perfect tense) A. has basado B. ha basado C. hemos basado D. he basado

  7. What does basar mean in English? A. to disturb B. to address as tú C. to base D. to be based on something yourself

  8. Which of these sentences is WRONG? A. Ayer, Yo basé mi decisión en los hechos. B. Yo basa mi opinión en los datos. C. Yo baso mi opinión en los datos. D. Él/Ella basa la teoría en la experiencia.

  9. Which is the gerund of basar, used with estar for the progressive? A. basando B. basado C. baso D. basé

  10. Which is the past participle of basar, used with haber in the perfect tenses? A. basando B. baso C. basé D. basado

Answer key

  1. basan — The correct form here is basan.
  2. basamos — The correct form here is basamos.
  3. basabas — The correct form here is basabas.
  4. basará — The correct form here is basará.
  5. basaríamos — The correct form here is basaríamos.
  6. he basado — The correct form here is he basado.
  7. to base — Basar means to base. Basarse means to be based on something yourself, which is a different verb.
  8. Yo basa mi opinión en los datos. — The first sentence is wrong: the correct form is Yo baso mi opinión en los datos.. The person matters: basa is the él/ella/Ud. form, while the yo form is baso. Using the third-person form with yo is one of the most common beginner errors.
  9. basando — The gerund of basar is basando: estoy basando.
  10. basado — The past participle of basar is basado: he basado, has basado, ha basado.

Frequently asked questions

What does basar mean?

Basar means to base. Basar means to base, and it is the transitive verb for founding an opinion, a theory, a decision or a project on something: you base your opinion on the data, you base a theory on experience. It takes en for the foundation, as in basar mi opinión en los datos.

When do people use basar most?

People use basar most in everyday situations such as Yo baso mi opinión en los datos. and Ayer, Yo basé mi decisión en los hechos.. Learn the present tense first, then the preterite and the imperfect, since those are the forms you will hear most often.

What is the difference between basar and basarse?

Basar means to base, while basarse means to be based on something yourself. They appear in similar situations, but they are not interchangeable — check the meaning you want before you choose.

How can I remember the forms of basar?

Practise the present tense table first, then add the preterite and the imperfect. Use the full conjugation of basar as your reference, the basar present tense page for one tense in depth, and the Spanish Verb Quiz to test yourself.

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