Yes in Portuguese is “Sim”, but since Brazilians pronounce the m’s at the end of words as n’s, Sim is pronounces as a nasally “si.” Yes = Sim, No = Não.
Something Odd About Yes in Portuguese
However, there is one thing about saying yes in Portuguese in Brazil that you should know about: Brazilians rarely say yes.
Instead of responding “sim” to yes/no questions, Brazilians prefer to respond by affirming the verb that was asked. For example, when asking questions such as “você vai ao cinema?” (“are you going to the movies?”) a Brazilian would respond: “vou” (I’m going). Another example: “você quer conversar?” (“do you want to talk?”), the appropriate response would be “quero” (I want). One more example. In response to the question “você podia lavar os pratos?” (“could you wash the dishes?”) a Brazilian Portuguese speaker would respond “posso” (I can) to mean yes.
It would not be incorrect to respond “sim” in Portuguese to answer any of the above questions.