Brazilian Portuguese Grammar

Subject

The subject is the doer of the action or state expressed by the verb, and it can be:

1. Simples, when the subject is made up of one single head, or composto, when made up of two or more heads;

2. Expresso, when the subject is clear (written) in the text, or oculto, when it is left out, indicated by verb endings;

3. Indeterminado, when it is impossible to ascertain who performed the action; otherwise, it is called determinado.

4. Inexistente, which appears in clauses called subjectless clauses.

5. Paciente, which constitutes the subject in passive voice sentences.

Portuguese	Analysis	English
Ayrton Senna era brasileiro.	Sujeito simples, expresso, determinado.	Ayrton Senna was Brazilian.
João e José são amigos desde a infância.	Sujeito composto, expresso, determinado.	João and José have been friends since chilhood.
Comprei um romance de Machado de Assis ontem. *the verb ending -ei* indicates 1st person singular, pretérito perfeito do indicativo.**	*Sujeito oculto, determinado*	I bought a novel by Machado de Assis yesterday
Roubaram minha bicicleta.	Sujeito indeterminado	They have robbed my bicycle or My bicycle has been robbed.
Precisa-se de empregados.	Sujeito indeterminado	Employees are wanted.
The sujeito indeterminado can only occur under the circumstances below: Verb in the 3rd person plural of verb tenses Verb in the 3rd person singular, followed by particle se, if the verb is requires a preposition (prepositional verb).
É verão.	*Sujeito inexistente*	It is summer.
Choveu muito hoje de manhã.		It rained a lot this morning.
Faz frio no inverno.		It's cold in the winter.
Está muito quente hoje.		It's very hot today.
São duas horas.		It's two o'clock
The *sujeito inexistente* occurs with verbs referring to the weather, verb ser + clock time, verb haver meaning existir (there to be) and verb fazer and estar + weather conditions. Unlike English, these sentences don't have a subject in Portuguese.
O avião foi inventado por Santos-Dumont.	sujeito paciente	The airplane was invented by Santos-Dumont.