I am confusing when learning portugues. Please help me. I am confusing when learning portugues. Please help me. For example 1. Trabalha no porto? Sim, trabalho num hospital no porto. 2. Onde é que você mora? Moro perto da universidade. I can’t understand when or where have to change the underlining letter. How to distinguish? Thank you very much. sorry, so careless i am. Trabalha & trabalho, mora & Moro, which are using in the sentences. I don't understand when to change 'a' to 'o' or 'o' to 'a' in the word. thank you