Sua - Tua
Both words mean de same? When I use each one? Obrigada
Tua is always related to "tu" (you). Sua is related to você (you), ele (he/it), ela (she/it). So, use seu/sua for 'its'. If you want a clear distiction among the uses of seu/sua, use dele/dela. The cat drinks its milk = o gato bebe o seu leite = o gato bebe o leite dele. The second option works better
Use "Sua" when you talk to someone that isn't close to you (when you speak formal). Like when you ask to a not so close person or a stranger how is his mother - "Como está a SUA mãe?".
You use "Tua" when you talk to someone close to you (when you speak informal). For exemple, when you ask a close friend how's his mother - "Como está a TUA mãe?". You talk like this in Portugal, in Brazil I think they change a little bit Hope i helped!