zeal comes from Late Latin zēlus ('zeal, ardor'), from Ancient Greek ζῆλος (zêlos, 'eager rivalry, jealousy, ardor'). The path is chiefly one of transmission: an older form is taken into English, with the word's shape and meaning carried through the language names and forms preserved in the history. In modern use, the noun sense is "great energy or enthusiasm in pursuit of a cause or objective", which keeps the etymology connected to the word's present dictionary value rather than treating it as a merely historical label. The wider word family includes related English forms such as jealous and derivatives such as zealous, zealot, zealotry, showing how the same base continues to support neighboring English vocabulary. The principal historical forms in the chain include Latin zēlus, Ancient Greek ζῆλος, which anchor the explanation in named linguistic material.