This is the 330th most frequent Croatian word.
tvrdi
"Hard" or "claims," depending on context.
The word "tvrdi" is used as a verb here, meaning "claims" or "states".
On tvrdi da je film bio odličan.
He claims that the movie was excellent.
In this context, "tvrdi" is used as an adjective, meaning "hard" or "solid".
Ploča je vrlo tvrdi materijal.
The board is a very hard material.
Here, "tvrdi" is again a verb, meaning "asserts".