The imperfect indicative can be used to create the past continuous tense (the past equivalent of the present continuous). As noted above, in English we often use the past continuous in places where the Portuguese would use the imperfect indicative, but the Portuguese still use the past continuous when they want to describe events that were ongoing in the past when something else happened (for example, ‘I was working when the postman called.’ – ‘Eu estava a trabalhar quando o carteiro chamou.’).
The past continuous is formed by taking the imperfect indicative of the verb ‘estar’ and adding ‘a’ + infinitive (or the present participle in Brazilian Portuguese) in the same way that the present continuous is formed with the present indiciative of ‘estar’. For example, ‘eu estava a trabalhar’. It can also be used in the subjunctive mood to convey uncertainty of action.
Full conjugations are given in the verb tables at the end of the book: