This is the 305th most frequent Portuguese word.
brasília
Brasília: Capital city of Brazil.
The word 'Brasília' is used as a proper noun, referring to the capital city of Brazil.
Brasília é a capital do Brasil.
Brasília is the capital of Brazil.
Here, 'Brasília' functions as a destination, again as a proper noun for the city.
Eu visitei Brasília nas minhas últimas férias.
I visited Brasília during my last vacation.
In this example, 'Brasília' is mentioned in context with its climatic conditions, still as a proper noun.