sustituir Imperfect Conjugation
sustituir — to replace
Sustituir is regular in the imperfect: sustituía, sustituías, sustituía, sustituíamos, sustituíais, sustituían.
sustituir Imperfect Forms
When to Use the Imperfect
Use the imperfect to describe a repeated replacement in the past or a situation where someone was acting as a substitute over an undefined period.
Notes on sustituir in the Imperfect
Sustituir is regular in the imperfect. Note that every single form carries an accent mark on the 'í'.
Example Sentences
De niño, yo sustituía los dulces por fruta.
As a child, I used to replace sweets with fruit.
yo
Ellos sustituían las piezas cada seis meses.
They used to replace the parts every six months.
ellos/ellas/ustedes
Common Mistakes
Mistake: Omitting the accent mark (sustituia).
Correct: sustituía
Why: All -ir verbs in the imperfect require an accent on the 'i' to maintain the correct stress and syllable structure.
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Related Tenses
Present
yo: sustituyo
Sustituir is irregular in the present tense, adding a 'y' before the ending in most forms: sustituyo, sustituyes, sustituye, sustituyen.
Preterite
yo: sustituí
In the preterite, sustituir changes 'i' to 'y' in the third-person forms: sustituyó and sustituyeron.
Future
yo: sustituiré
The future of sustituir is regular: just add endings to the infinitive (sustituiré, sustituirás).
Conditional
yo: sustituiría
The conditional is regular: add -ía endings to the infinitive 'sustituir'.
Present Subjunctive
yo: sustituya
The present subjunctive follows the 'yo' form of the present indicative, adding a 'y': sustituya, sustituyas, etc.
Imperfect Subjunctive
yo: sustituyera
The imperfect subjunctive is built from the 'sustituyeron' stem: sustituyera, sustituyeras, etc.
Affirmative Imperative
yo: sustituye
Give commands to replace things: sustituye (tú), sustituya (usted), sustituyamos (nosotros).
Negative Imperative
yo: no sustituyas
Negative commands use the present subjunctive forms: no sustituyas, no sustituya.