sustituí

Sustituí is the first-person singular form of the Spanish verb sustituir in the preterite indicative, meaning “I substituted” or “I replaced.” It marks a completed action in the past in which one thing was replaced by another.

Conjugation in the preterite: yo sustit u í, tú sustituiste, él sustituyó, nosotros sustituimos, vosotros sustituisteis, ellos sustituyeron. Note that the third-person forms include a written accent and, in plural, a y: él sustituyó, ellos sustituyeron. The stem is sustitu-, and the endings correspond to the pretérito for -uir verbs, with the relevant orthographic marks.

Usage and meaning: Sustituir is used to express replacing someone or something with another. The common construction is sustituir A por B (to substitute A for B). It can also describe substituting a person in a role or task, as in “Yo sustituí al profesor ausente.” The preterite form sustitutí situates the action at a specific past moment, distinguishing it from present or imperfect substitutions.

Etymology and related forms: Sustituir comes from Latin substituere, via the Spanish evolution of -uir verbs. Related forms include the present tense sustituyo, sustituyes, sustituye, sustituyamos, sustituyen; the gerund sustituyendo; and the past participle sustituido. In many contexts, substitutes or replacements are discussed with synonyms such as reemplazar or suplir, though sustituir emphasizes the act of substitution itself.