tverdyi
Tverdyi is a transliteration of the Russian adjective твёрдый, meaning hard, solid, or firm. It is used to describe physical properties of objects as well as figurative qualities such as resolve or conviction. For example, твердый камень means a hard stone, твердый металл a hard metal, and твёрдое убеждение a firm conviction. The adverb form is твёрдо, meaning “firmly.”
Etymology and cognates: The word derives from Proto-Slavic *tvьrdъ and has cognates in several Slavic languages,
Morphology: In Russian, твёрдый inflects for gender, number, and case. The basic forms are masculine твёрдый, feminine твёрдая, neuter
Usage notes: The term is common in technical, scientific, and everyday language. It often contrasts with мягкий
See also: twardy (Polish), tv́erdiy (Ukrainian), tvrdy (Czech), твёрдость (firmness), твёрдо (firmly).