An ethic is a guiding moral principle. A work ethic, a professional ethic, an ethic of care.
The singular means one principle and the plural, ethics, means the whole field or a code — and ethics takes a singular verb when it means the study. Work ethic is much the commonest use and means the belief that hard work is a virtue in itself.
1nounethicA guiding moral principle.
“The team's strong ethic of fair play earned them respect from their rivals.”
ethic is a principle.
Greek ethikos comes from ethos, character or custom.
Proto-Indo-European
*dʰeh₁-
Ancient Greek
ἠθῐκός
Latin
ēthicus
Middle English
etik
English, today
ethic
From Middle English etik, from Latin ēthicus, from Ancient Greek ἠθῐκός.
Etymology from Wiktionary, CC BY-SA