This is the 146th most frequent Slovak word.
tvrdí
"Tvrdí" in English means "claims" or "asserts."
In this sentence, 'tvrdí' is used as a verb meaning 'claims' or 'asserts,' indicating that someone is stating something as a fact.
On tvrdí, že má pravdu.
He claims that he is right.
Here, 'tvrdí' refers to the book's content making a claim or statement about a certain topic.
Táto kniha tvrdí, že vesmír je nekonečný.
This book asserts that the universe is infinite.
In this context, 'tvrdí' is used to describe a recurring behavior of making contrary statements.