This is the 40th most frequent Portuguese word.
mil
"Mil" means "thousand" in English.
Here, 'mil' is used as a numeric adjective meaning 'thousand.'
Ele doou mil livros para a biblioteca.
He donated a thousand books to the library.
In this sentence, 'mil' is used figuratively to denote an uncountable or infinite number, expressing a general notion of very many.
Há mil maneiras de resolver esse problema.
There are a thousand ways to solve this problem.
Here, 'mil' works in conjunction with the word 'um' to form 'um mil,' specifying the number 1,000 in a formal count.