This is the 579th most frequent Lithuanian word.
tvirtina
Tvirtina - affirms, confirms, or asserts.
Here, 'tvirtina' is used to mean 'asserts' or 'claims', indicating that the subject is expressing a firm opinion or conviction.
Jis tvirtina, kad yra teisus.
He asserts that he is right.
Here, 'tvirtina' is utilized in the meaning of 'reinforce' or 'strengthen', referring to the act of making something more robust or secure.
Štai kaip jie tvirtina pastatus nuo žemės drebėjimų.
This is how they reinforce buildings against earthquakes.
In this sentence, 'tvirtina' carries the sense of 'states' or 'emphasizes', showing a strong confirmation or declaration from the subject.