"It is true."
Truth = verdade, true = verdadeiro. This expression in Portuguese differs from English. We say "é verdade". "é verdadeiro" is used, for instance, for original brands.
That always bothered me a bit, isn't it technically incorrect? Shouldn't it either be "é a verdade" or "é verdadeiro"?
I understand that "é verdade" is idiomatic, my question is more if it can be generalized to other nouns. Can I say for instance "é tristeza" or "é vergonha"?
I think this is a particular case for "verdade", as you should use "é triste" and "é vergonhoso".
"É verdadeiro" is also right, but it is used in another context: "It's genuine/legitimate".
Maybe that's why we use "é verdade" to mean "it's true".