demostrar Imperfect Conjugation
demostrar — to prove
Demostrar is regular in the imperfect: demostraba, demostrabas, demostraba, demostrábamos, demostrabais, demostraban.
demostrar Imperfect Forms
When to Use the Imperfect
Use the imperfect to describe a time in the past when someone 'used to' demonstrate a quality or when they were in the middle of proving something.
Notes on demostrar in the Imperfect
The imperfect is completely regular. It uses the standard -aba endings for -ar verbs.
Example Sentences
De niño, él siempre demostraba mucho talento para el piano.
As a child, he always demonstrated a lot of talent for the piano.
él/ella/usted
Mientras yo demostraba el software, se fue la luz.
While I was demonstrating the software, the power went out.
yo
Common Mistakes
Mistake: demuestraba
Correct: demostraba
Why: There is no 'ue' stem change in the imperfect tense for any Spanish verb.
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Related Tenses
Present
yo: demuestro
Demostrar is an o > ue stem-changing verb in all forms except nosotros and vosotros.
Preterite
yo: demostré
Demostrar is regular in the preterite: demostré, demostraste, demostró, demostramos, demostrasteis, demostraron.
Future
yo: demostraré
The future of demostrar is regular: demostraré, demostrarás, demostrará, demostraremos, demostraréis, demostrarán.
Conditional
yo: demostraría
The conditional of demostrar is regular: demostraría, demostrarías, demostraría, demostraríamos, demostraríais, demostrarían.
Present Subjunctive
yo: demuestre
Demostrar has a stem change (o > ue) in the subjunctive, except for nosotros and vosotros.
Imperfect Subjunctive
yo: demostrara
The imperfect subjunctive is regular: demostrara, demostraras, demostrara, demostráramos, demostrarais, demostraran.
Affirmative Imperative
yo: demuestra
The imperative uses 'demuestra' (tú) and 'demuestre' (usted), following the o > ue stem change.
Negative Imperative
yo: no demuestres
The negative imperative uses the present subjunctive: no demuestres, no demuestre, no demostremos, no demostréis, no demuestren.