tão

tão

"So" or "as" (used to indicate degree or intensity).

In this sentence, "tão" is used to establish a comparison indicating equality or similarity, as in "as...as."

Ele é tão rápido quanto um carro.

He is as fast as a car.

Here, "tão" is utilized as an intensifier to amplify the adjective "cansado," meaning "so."

Estou tão cansado hoje que vou dormir cedo.

I am so tired today that I will go to bed early.

In this case, "tão" emphasizes the adjective "serious," conveying the sense of "that."

Não precisa ser tão sério o tempo todo.

You don't need to be that serious all the time.