Here's how it works:
* "Obrigado" is used by men.
* "Obrigada" is used by women.
* "Obrigado" is also used when addressing a group of people, regardless of gender.
You can also use "muito obrigado" or "muito obrigada" to express "thank you very much".
Here are some examples:
* "Obrigado pelo seu tempo." (Thank you for your time.)
* "Obrigada pela ajuda." (Thank you for your help.)
* "Muito obrigado pela refeição." (Thank you very much for the meal.)
* "Obrigado a todos!" (Thank you everyone!)