Describe the rules for forming the pluperfect tense in Portuguese and provide examples.

The pluperfect tense, also known as the past perfect tense, is used in Portuguese to express actions or events that occurred before another past action or time point. It emphasizes the completion of an action in the past before another action took place. Let's delve into the rules for forming the pluperfect tense in Portuguese and provide examples to illustrate its usage.

To form the pluperfect tense in Portuguese, you need to follow these rules:

1. Conjugation of the auxiliary verb "ter" (to have):

* The auxiliary verb "ter" is conjugated in the imperfect past tense according to the subject of the sentence. Here are its conjugations:
Eu tinha (I had)
Tu tinhas (You had)
Ele/Ela/Você tinha (He/She/You had)
Nós tínhamos (We had)
Vós tínheis (You all had)
Eles/Elas/Vocês tinham (They/You all had)
2. Past participle agreement:

* The past participle of the main verb agrees in gender and number with the subject of the sentence, just like in the compound tenses. If the subject is masculine singular, the past participle remains in its regular form. If the subject is feminine singular, an "a" is added to the end of the past participle. If the subject is plural, an "s" is added to the end of the past participle.

Now let's see some examples of the pluperfect tense in Portuguese:

1. Eu tinha estudado antes de chegar à aula.
(I had studied before arriving at the class.)
2. Quando ele chegou, eu já tinha saído.
(When he arrived, I had already left.)
3. Ela tinha terminado a tarefa quando o professor pediu para entregar.
(She had finished the task when the teacher asked to hand it in.)
4. Nós tínhamos comido quando você chegou ao restaurante.
(We had eaten when you arrived at the restaurant.)
5. Eles tinham viajado para o exterior antes de conhecerem o novo colega.
(They had traveled abroad before meeting the new colleague.)

In these examples, you can observe the combination of the imperfect past form of the auxiliary verb "ter" with the past participle of the main verb. This construction allows us to express an action that was completed in the past before another action occurred.

By understanding and practicing the formation of the pluperfect tense, learners of Portuguese can convey past events in a precise and nuanced manner, highlighting the sequence of actions and emphasizing the completion of actions before a specific past reference point.