A voz passiva
When the focus shifts from who acts to who is acted upon, Portuguese uses the voz passiva: ser + past participle (+ por / pelo / pela for the agent). O livro foi escrito por Saramago = The book was written by Saramago. The participle agrees with the subject like an adjective. Portuguese also has a slick alternative — the se passivo / impersonal se — which sidesteps the agent entirely: vende-se casa = house for sale.
The structure — ser + past participle
The basic frame is subject + ser (in any tense) + past participle + optional por/pelo/pela + agent. The participle agrees with the subject in gender and number — exactly like an adjective. A carta foi escrita pelo João = The letter was written by João (escrita agrees with carta, f.sg.). Os livros foram lidos pelos alunos = The books were read by the students (lidos, m.pl.). Tense lives in ser: é vendido (present), foi vendido (pretérito), era vendido (imperfeito), será vendido (futuro), seria vendido (condicional), tinha sido vendido (mais-que-perfeito), teria sido vendido (condicional composto). Estar + participle exists too but means a STATE, not an action: a porta está fechada = the door is closed (state), vs. a porta foi fechada pelo vento = the door was closed by the wind (action).
The agent — por / pelo / pela
The agent (the one who does the action) is introduced by por, which contracts with the article: por + o = pelo, por + a = pela, por + os = pelos, por + as = pelas. A casa foi construída pelo arquiteto = The house was built by the architect. A música foi composta pela Amélia = The song was composed by Amélia. Os documentos foram assinados pelos ministros = The documents were signed by the ministers. The agent can be omitted when it's unknown, obvious, or irrelevant: A loja foi assaltada (the store was robbed — by whom we don't say). PT and BR identical here.
Participle agreement — the gender/number dance
Unlike the past participle in ter + part. (lesson 29, INVARIABLE), the participle in ser + part. AGREES with the subject. O bolo foi feito pela avó (m.sg. feito). A sopa foi feita pela avó (f.sg. feita). Os bolos foram feitos (m.pl.). As sopas foram feitas (f.pl.). Some participles have two forms — a regular one for ter and a short one for ser/estar: aceitar → aceitado (with ter) / aceite in PT, aceito in BR (with ser/estar). entregar → entregado / entregue. pagar → pagado / pago. ganhar → ganhado / ganho (BR more often ganho in both contexts). Ele tinha pagado a conta but a conta foi paga. Ele tinha entregado o livro but o livro foi entregue. The 'short' form behaves more like an adjective; the 'long' form is the verbal one.
Se passivo — the impersonal alternative
Portuguese has a second passive construction with se that's extremely common, especially with inanimate subjects. It looks like a reflexive but acts as a passive. Vendem-se casas = houses are sold (lit. 'houses sell themselves'). Aluga-se quarto = room for rent. Fala-se inglês = English is spoken (here). The verb agrees with the (inanimate) subject in number: singular subject → singular verb, plural subject → plural verb. Construiu-se a casa em 1900 (sg.) vs. Construíram-se as casas em 1900 (pl.). The agent CAN'T be expressed in this construction — that's the point: it's deliberately faceless. PT writing prefers vendem-se casas; BR writing tends to keep it singular (vende-se casas) — the BR usage is grammatically debated but very widespread.
Impersonal se vs. se passivo — the line
When the verb is INTRANSITIVE (no object) or the subject is a person, se is properly impersonal and the verb stays singular. Aqui vive-se bem = one lives well here / life is good here (intransitive — singular). Precisa-se de empregados = employees are needed (with de — preposition glues to se). With transitive verbs and an inanimate subject, the se passivo kicks in and the verb agrees in number with the subject: Vendem-se casas. The distinction is a fine one and even native speakers blur it; the safe rules of thumb are: (1) inanimate subject + transitive verb + no agent = se passivo with agreement, (2) general 'one / you / people' = impersonal se with singular verb. In speech and even in writing, agreement gets shaky — vende-se carros is heard everywhere despite being prescriptively wrong.
When to use which — and the BR drift
Full passive (ser + part.) is reserved for sentences where the agent matters or the focus is squarely on the patient: news headlines (O ladrão foi preso pela polícia), formal narration (O contrato foi assinado por ambas as partes). The se passivo dominates everyday descriptions of products, services, and signs (vende-se, aluga-se, precisa-se de, fala-se inglês). BR speakers also reach more often for an active 3rd-plural construction with no explicit subject: assaltaram a loja (lit. they robbed the store) replacing a loja foi assaltada. PT has this option too but is less drawn to it. In B1 writing, recognize and use both passive constructions; in B1 speech, the se passivo is the high-frequency pattern to drill.
