The word 'theist' is a modern construction built from classical components. Its core, the-, originates from the ancient Greek noun theos, meaning "a god or deity". This root is combined with the agent suffix -ist, derived from Greek -istēs, which denotes a person who practices or holds a specific belief. The term was systematically formed in the 17th century during philosophical and theological debates to precisely label someone who maintains a belief in a personal, intervening God, as distinct from a deist. Thus, the word's logic is transparent: it literally means "one who holds a belief in god(s)".

Structure: the (god) + ist (person who believes in/practices) - the: From Greek theos, meaning "god, deity". Functions as the core root conveying the concept of divinity. - ist: From Greek -istēs, via Latin -ista, a suffix forming agent nouns, meaning "one who practices or believes in". Functions as a derivational suffix denoting a person adhering to a doctrine.