What this suffix does
-nomy and its variant -omy come from Greek nomos (law, custom, distribution) and form nouns that describe a system of organized knowledge, rules, or management governing a field. Astronomy (the ordering of the stars), economy (the management of a household, extended to state finances), taxonomy (the laws of classification), gastronomy (the art of good eating), autonomy (self-law, self-governance) — each uses the root to describe a coherent system with its own internal logic. These words appear across the sciences, social sciences, arts, and everyday life, making -nomy one of the most productive roots in English.