tvrdoe
Tvrdoe is the transliteration commonly used in English-language discussions for the neuter singular form of the Slavic adjective твёрдое, meaning hard, firm, or solid. In Russian and other Cyrillic-script languages, tvrdoe appears before neuter nouns to describe a quality as in твёрдое стекло (hard glass) or твёрдое тело (a hard body). The form is one of several gendered and inflected forms of the root tvr- that expresses hardness or solidity.
Etymology and related forms are rooted in the Slavic verb and adjective system. The base root tvr-
Usage and scope. In linguistic, philological, and technical contexts, tvrdoe appears primarily as a grammatical form
Notes and clarification. Tvrdoe should not be confused with other language-specific permutations of the root meaning
In summary, tvrdoe denotes the neuter form of the Slavic root meaning hard, primarily appearing in Cyrillic-origin