Obrigado - how to express your gratitude in Portuguese
by João Rosa
I'm Portuguese, and in my culture it is very important to thank other people when they do something for you, even if they are just doing their job. I've seen how this sometimes baffles some foreigners - "Why are you thanking him, he's just doing his job!" - well, if you don't, you'll be considered rude and may expect a degradation of that person's service in the future.
There are many ways to say "thank you" in Portuguese, that vary in formality and degree of gratitude:
obrigado/a - thank you, informal
muito obrigado/a - thank you very much
obrigadinho/a - kindly thank you, friendly, you should smile when using this form, or be misinterpreted as being ironic/angry: thanks for nothing/thanks, but no thanks
muitíssimo obrigado/a - thank you very, very much, I owe you, somewhat formal
obrigadíssimo/a - thank you very, very much, I owe you, somewhat formal
agradecido/a(s) - thank you, formal
muito agradecido/a(s) - thank you very much, formal
muitíssimo agradecido/a(s) - thank you very, very much, I owe you, formal
agradecidíssimo/a(s) - thank you very, very much, I owe you, formal
agradeço-te - thank you deeply, to a friend/coworker/colleague, formal
agradeço-lhe - thank you deeply, to a superior/stranger, formal
agradeço-vos - thank you deeply, to 2 or more people, formal
grato/a(s) - thank you, very formal
muito grato/a(s) - thank you very much, very formal
muitíssimo grato/a(s) - thank you very, very much, I owe you, very formal
gratíssimo/a(s) - thank you very, very much, I owe you, very formal
Notes on gender and number
The "o" ending is used by males when giving thanks, e.g. obrigado. Females use the "a" ending, e.g. obrigada. If you are saying thanks in the name of a group of males, a mixed sex group or a collective entity - like a corporation to a client: you use the "os" ending, e.g. obrigados. When you say thanks in the name a group of females, you use the "as" ending, e.g. obrigadas.
Notes on saying thank you in Brazil
by Marcelo Luiz
In Brazil we use:
Obrigado/a! (formal)
Muito obrigado/a! (formal)
Muito agradecido/a (formal)
Grato/a por/pelo(s)/pela(s)... (formal)
'brigado/a! (informal)- the first "o" is not pronounced.
Obrigadão! (informal)
Valeu! (very informal)
Obrigados and obrigadas are not normally used in Brazil.