Regii

Regii is not an English term but a Latin inflected form. It serves as the genitive singular of the adjective regius, which means royal or kingly. In Latin, adjectives decline to agree with the nouns they modify, so regius has a genitive singular form regii, which would translate roughly as “of the king” or “of the royal” depending on context and the gender of the noun being described.

Etymology and meaning: regius comes from the Latin root reg-, related to rex, king. That root appears in many related words such as regal, regime, and region. The genitive singular regii is one of several forms that the adjective can take in different gender and number, and it would typically appear in phrases where a noun is implied or in inscriptions and older texts.

Usage and context: regii is primarily encountered within Latin texts or grammars as a grammatical form rather than as an independent English vocabulary item. In actual Latin prose, a speaker would more often use regius with a fully expressed noun (for example, regius rex or regius thesaurus) or would employ the standard genitive of rex (regis) to indicate possession. When regii does appear, it signals a masculine or neuter noun in the genitive singular, i.e., something belonging to or associated with the king or royal authority.

In modern reference works, regii is cited chiefly in discussions of Latin morphology rather than in everyday usage. See also regius, rex, and regal for related terms describing kingship or royal status.