sustituían

Sustituían is the third-person plural form of the verb sustituir in the pretérito imperfecto de indicativo. It describes a past action that was habitual, repeated, or ongoing, corresponding to “they used to substitute” or “they were substituting” in English. The subject is usually ellos, ellas, or ustedes, and the form is regular within the imperfect conjugation of -ir verbs.

Etymology and meaning: sustituir comes from the Latin substituere, formed by sub- “under, in place of” and statuere “to place, to set.” In Spanish, it acquired the sense of replacing one person or thing with another, with nuances of temporary or ongoing replacement in the past.

Usage notes: Sustituían is common in narrative or descriptive past contexts to indicate substitution over time, such as personnel changes, replacements in teams, or interim replacements in institutions. It contrasts with sustituyeron (preterite, completed substitution) and with sustituye (present tense). The verb can take a direct object referring to the person or thing being substituted (e.g., a worker, a player) and, when needed, pronouns or phrases can be added for clarity.

Examples:

- Sustituían a los trabajadores que estaban de permiso.

- En los partidos, los suplentes sustituían a los jugadores lesionados.

- Durante años, los docentes sustitúían a los maestros ausentes.

See also: sustitución, sustituto, sustituible, sustitutivo.