The second person singular form (you) in Portuguese is only used informally – i.e., with people you know very well, family members, children, or those considerably younger than yourself. To express a verb in the second person singular form formally, you actually use the third person singular form of the verb. When you think about it, this makes sense, because as you have already seen, the polite Portuguese word for ‘you’ is the equivalent of saying ‘the lady’ or ‘the gentleman’ – so you are actually using the third person anyway (for example, to politely say ‘you work’, you are effectively saying ‘the lady/gentleman works’ – so the verb ‘to work’ is expressed in the third person singular form ‘works’).
As has already been mentioned, the English language no longer differentiates between singular and plural forms of the second person (‘you…’). Portuguese is similar, in that the second person plural form is very rarely used nowadays. Instead of this, the third person plural is usually used – so to say that ‘you (plural) do something’ is effectively the same as saying ‘they do something’. You might occasionally find the old second person plural form in literature, so is worth knowing about, but it is rare to hear it in spoken Portuguese.
In many cases, it is obvious from the verb ending who is performing the action, so it is sometimes unnecessary to use the equivalent of the pronouns ‘I’, ‘we’, or ‘you’. To say ‘I work’, you can just say one word in Portuguese: ‘trabalho’. Likewise, to say ‘we work’, you just need one word: ‘trabalhamos’. However, if you want to emphasise who is doing the work, you do use the pronoun. For example, to say ‘I work, but he doesn't work’ in Portuguese (with the emphasis on ‘I’ and ‘he’), it is necessary to use the Portuguese equivalents of the pronouns ‘I’ and ‘he’ (‘eu’ and ‘ele’) – ‘Eu trabalho mas ele não trabalha’.
If you prefer, it will not sound wrong if you use pronouns all of the time, like we do in English – you just need to be aware that it is not always necessary, so that you can understand what others say.
