substituam

Substituam is a Portuguese verb form derived from substituir, meaning to substitute or replace. It serves as the present subjunctive form for the third-person plural (eles/elas) and as the imperative form for the second-person plural (vocês). This dual function is common in Portuguese, where the same spelling can appear in different grammatical moods or voices.

Etymology and form: The verb substituir comes from Latin substituere, literally “to place in place of.” In Portuguese it developed through the medieval and modern stages as a regular -ir verb with a stem substitute in subjunctive constructions. The form substituam is characteristic of the present subjunctive for eles/elas and of the imperative for vocês.

Grammar and usage: In the present subjunctive, substituam appears in subordinate clauses after verbs of desire, doubt, necessity, or after conjunctions such as que, para que, embora, etc. Examples: É essencial que eles substituam as peças defeituosas. Que vocês substituam os elementos problemáticos é necessário. In the imperative, substituam is used to give a direct instruction to a group: Substituam os componentes antes de ligar o equipamento.

Relation to related forms: The verb substituír is irregular in the present indicative (eu substituo, tu substituis, ele substitui, nós substituímos, vós substituís, eles substituem), but the present subjunctive form substituam follows the regular subjunctive pattern for -ir verbs in the terceira pessoa do plural. Synonyms and related verbs include trocar, substituir, trocar por: to replace or swap.

Notes: Substituam can be ambiguous without context, because it may function as an imperative for vocês or as a present subjunctive form after certain verbs or conjunctions.