Demostrar Present Tense Conjugation in Spanish
The present tense of demostrar — "to demonstrate" in English — is the form you need for what happens now, for habits and for general truths. This page gives you the full present conjugation table for demostrar with all six persons, explains exactly how the tense is formed for this verb, shows when to use it with real examples, and finishes with a quiz so you can test yourself. Demostrar means to demonstrate or to prove: you demonstrate a theory with evidence, or you demonstrate a feeling with actions. It is stronger and more formal than mostrar. To see it in a real sentence: Yo demuestro su talento en el escenario — "I demonstrate his talent on stage".
Present tense conjugation table: demostrar
Every person of demostrar in the present tense. The gerund is demostrando and the past participle is demostrado.
| Person | Form |
|---|---|
| yo | demuestro |
| tú | demuestras |
| él/ella/Ud. | demuestra |
| nosotros/as | demostramos |
| vosotros/as | demostráis |
| ellos/ellas/Uds. | demuestran |
How the present of demostrar is formed
The present of demostrar is built from the stem demostr- plus the present endings for -ar verbs. Take the infinitive, drop the -ar ending, and add the ending that matches the person. The table below shows the endings, and the full table above shows them attached to the stem.
| Person | Ending | Form |
|---|---|---|
| yo | -o | demuestro |
| tú | -as | demuestras |
| él/ella/Ud. | -a | demuestra |
| nosotros/as | -amos | demostramos |
| vosotros/as | -áis | demostráis |
| ellos/ellas/Uds. | -an | demuestran |
The stem vowel changes in the stressed forms of the present: demuestro, demuestras, demuestra and demuestran — but nosotros and vosotros keep the plain stem: demostramos, demostráis.
The gerund of demostrar is demostrando and the past participle is demostrado. Both are the forms you need with estar and haber respectively.
When to use the present tense of demostrar
The present tense is not one single use — it covers several situations, and demostrar appears in all of them. The five uses below are the ones you will meet most often, each with an example that shows the verb in a natural sentence.
Habits and routines
The present describes things that happen regularly, as a habit or routine.
"Cada día, yo demuestro su talento en el escenario" — "Every day, I demonstrate his talent on stage"
General truths
The present states facts that are always true, not just true today.
"Mi amigo demuestra la teoría con un experimento" — "My friend demonstrates the theory with an experiment"
What is happening now
The present describes an action in progress right now.
"Ahora, yo demuestro su afecto con un regalo" — "Right now, I demonstrate his affection with a gift"
Near-future plans
Spanish often uses the present for a plan that is already fixed.
"Mañana, nosotros demostramos su inocencia ante el juez" — "Tomorrow, we demonstrate his innocence before the judge"
Timetables and scheduled events
The present is the tense for timetables, programmes and things that happen on a schedule.
"Ellos demuestran interés por el proyecto" — "They demonstrate interest in the project"
The present tense vs the closest tenses
Present — habit or general fact vs Preterite — one finished occasion
The present describes a habit, a routine or a general fact — something that happens again and again or that is true in general. The preterite reports one finished occasion in the past. Use the present when the action repeats or is still true, and the preterite when you are telling what happened once, on a specific day.
- Present — habit or general fact: {'pre_es': 'Cada día, ', 'pre_en': 'Every day, '}yo demuestro su talento en el escenario — "I demonstrate his talent on stage"
- Preterite — one finished occasion: {'pre_es': 'Ayer, ', 'pre_en': 'Yesterday, '}yo demostré su talento en el escenario — "I demonstrated his talent on stage"
Present — now vs Imperfect — a past habit or background
The present talks about now. The imperfect talks about the past as a background — a repeated habit, an ongoing situation, something that used to happen. If you can add "used to" in English, the imperfect is usually the right choice; if it is happening now or always, use the present.
- Present — now: {}tú demuestras la teoría con un experimento — "You demonstrate the theory with an experiment"
- Imperfect — a past habit or background: {}tú demostrabas la teoría con un experimento — "You used to demonstrate the theory with an experiment"
Present — now or a fixed plan vs Future — what will happen
The present describes what happens now, what you do regularly, or a plan that is already fixed. The future describes what will happen later — a promise, a prediction, a plan that is not yet under way. Spanish often uses the present for near-future plans, but the future is the form for a clear statement about tomorrow.
- Present — now or a fixed plan: {'subj_es': 'Mi amigo', 'subj_en': 'My friend'}él demuestra su afecto con un regalo — "He demonstrates his affection with a gift"
- Future — what will happen: {'subj_es': 'Mi amigo', 'subj_en': 'My friend'}él demostrará su afecto con un regalo — "He will demonstrate his affection with a gift"
Examples: demostrar in the present tense
Seven sentences that show demostrar in the present tense only, across all six persons. Read each one aloud, notice the ending, and check the translation.
- Yo demuestro su talento en el escenario — "I demonstrate his talent on stage"
- Tú demuestras la teoría con un experimento — "You demonstrate the theory with an experiment"
- Él demuestra su afecto con un regalo — "He demonstrates his affection with a gift"
- Nosotros demostramos su inocencia ante el juez — "We demonstrate his innocence before the judge"
- Vosotros demostráis interés por el proyecto — "You demonstrate interest in the project"
- Ellos demuestran su talento en el escenario — "They demonstrate his talent on stage"
- Yo demuestro la teoría con un experimento — "I demonstrate the theory with an experiment"
Common mistakes with demostrar in the present tense
These are the errors learners actually make with demostrar in the present tense. Each one shows the wrong form, the right form, and why the right form is right.
✗ *Yo demostro su talento en el escenario.
✓ Correct: Yo demuestro su talento en el escenario.
demostrar is a stem-changing verb (o → ue): the stem vowel changes in the stressed present forms, so the yo form is demuestro, not demostro.
✗ *Tú demuestra la teoría con un experimento.
✓ Correct: Tú demuestras la teoría con un experimento.
The tú form and the él form are different: tú takes demuestras, él takes demuestra.
✗ *Cada día, yo demostré su afecto con un regalo
✓ Correct: Cada día, yo demuestro su afecto con un regalo
Cada día describes a habit, so it needs the present, not the preterite.
✗ *Vosotros demostrais su inocencia ante el juez.
✓ Correct: Vosotros demostráis su inocencia ante el juez.
The vosotros present form carries a written accent: demostráis, not demostrais.
Quiz: demostrar in the present tense
Eight questions on the present tense of demostrar. Choose the best answer for each one, then check the answer key below — every answer is explained.
Which is the correct present form of demostrar for tú? A. demuestro B. demuestra C. demostramos D. demuestras
Complete the sentence: Yo ______ su talento en el escenario — "I demonstrate his talent on stage" (present) A. demuestras B. demuestra C. demostramos D. demuestro
Complete the sentence: Él ______ la teoría con un experimento — "He demonstrates the theory with an experiment" (present) A. demuestra B. demuestro C. demuestras D. demostramos
Which is the correct present form of demostrar for nosotros? A. demuestra B. demuestran C. demostramos D. demuestras
Which sentence uses demostrar correctly in the present? A. Mi amigo demuestra su afecto con un regalo B. Mi amigo demuestras su afecto con un regalo C. Mi amigo demostraba su afecto con un regalo D. Mi amigo demostramos su afecto con un regalo
Complete the sentence: Vosotros ______ su inocencia ante el juez — "You demonstrate his innocence before the judge" (present) A. demostráis B. demuestro C. demuestras D. demuestra
Complete the sentence: Ellos ______ interés por el proyecto — "They demonstrate interest in the project" (present) A. demuestras B. demuestra C. demuestran D. demuestro
What is the gerund of demostrar? A. demostré B. demostrando C. demostrado D. demuestro
Answer key
- demuestras — The tú form in the present is demuestras.
- demuestro — The present form for yo is demuestro.
- demuestra — The present form for él/ella/Ud. is demuestra.
- demostramos — The nosotros form in the present is demostramos.
- Mi amigo demuestra su afecto con un regalo — Mi amigo demuestra su afecto con un regalo is correct: the verb agrees with its subject and the tense is the present.
- demostráis — The present form for vosotros/as is demostráis.
- demuestran — The present form for ellos/ellas/Uds. is demuestran.
- demostrando — The gerund is demostrando. It is the form you use with estar for the progressive, and it is not the past participle demostrado.
Frequently asked questions
Is demostrar regular in the present tense?
No — in the present the stem changes: The stem vowel changes in the stressed forms of the present: demuestro, demuestras, demuestra and demuestran — but nosotros and vosotros keep the plain stem: demostramos, demostráis. The nosotros and vosotros forms keep the plain stem.
What is the gerund and the past participle of demostrar?
The gerund is demostrando and the past participle is demostrado. Use the gerund with estar for the progressive, and the participle with haber for the perfect tenses.
How do you say "I demonstrate" in the present tense?
Say demuestro. For example: Yo demuestro su talento en el escenario — "I demonstrate his talent on stage".
What is the difference between the present and the preterite of demostrar?
The present describes a habit or what happens now: Yo demuestro su talento en el escenario — "I demonstrate his talent on stage". The preterite reports one finished occasion: Ayer, yo demostré su talento en el escenario — "Yesterday, I demonstrated his talent on stage". Use the present when the action repeats or is still true, and the preterite when you are telling what happened once.
Related links
- Full conjugation of demostrar — every tense and mood, with the complete tables.
- demostrar examples and quiz — more sentences, dialogues and a longer quiz.
- Spanish Present tense guide — how the present tense works for all Spanish verbs.
- Spanish verbs — the full list of Spanish verbs on VerbFlow.