Inklingo
A friendly scientist character pointing confidently at a large, clear chart displaying a successful outcome, proving a point to a colleague who looks satisfied.

demostrar Preterite Conjugation

demostrarto prove

A2irregular (o > ue stem change) -ar★★★★★
Quick answer:

Demostrar is regular in the preterite: demostré, demostraste, demostró, demostramos, demostrasteis, demostraron.

demostrar Preterite Forms

yodemostré
demostraste
él/ella/usteddemostró
nosotrosdemostramos
vosotrosdemostrasteis
ellos/ellas/ustedesdemostraron

When to Use the Preterite

Use the preterite to talk about a specific instance where someone proved or demonstrated something, like a scientific result or a point in an argument that is now finished.

Notes on demostrar in the Preterite

Unlike the present tense, demostrar is completely regular in the preterite. There is no 'o' to 'ue' stem change here.

Example Sentences

  • El científico demostró su teoría con un experimento.

    The scientist proved his theory with an experiment.

    él/ella/usted

  • Ayer les demostré que yo tenía razón.

    Yesterday I proved to them that I was right.

    yo

  • Los estudiantes demostraron sus habilidades en el examen.

    The students demonstrated their skills in the exam.

    ellos/ellas/ustedes

Common Mistakes

  • Mistake: demuestré

    Correct: demostré

    Why: Learners often try to carry the 'ue' stem change from the present tense into the preterite, but it doesn't belong here.

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