-ology is from the infinitive Logos which means 'to study'. It is understood that -ology is "the science or study of" a certain subject.
-onomy is from the Greek: Nomos, meaning law. Other sites say the suffix means "knowledge of"
The Concise Oxford defines '-logy' as denoting a subject of study or interest (much the same as above). It defines '-nomy' as denoting a specified area of knowledge or its laws (again, much like the above).
My opinion, which I have no good evidence for, is that '-nomy- denotes the observation of things as they are: Astronomy looks at the laws of the stars (the constellations and their movements). '-logy' is the practice of the subject: Astrology extrapolates "meaning" (if you believe that sort of thing) from the stars position. Gastroenterology or Radiology puts into practice what they know of a subject to give a result.
Egg-onomy.
Economy
agronomy. astronomy. autonomy. deuteronomy. economy. gastronomy. taxonomy. troponomy.
The suffix "nomy" comes from nomos, a greek work meaning "to regulate or arrange". Astronomy is a word derived from the Greek words "ASTRO" (star) and "NOMOS".
List of SuffixesCommon SuffixWord EndingExamples & List of Common Suffixes-able-ad-ade-age-agogy-al-al-ality-an-ance-ancy-ant-ant-ar-ar-ard-ary-ary-arch-archy-ate-ate-ate-athlon-ation-ative-atory-bound-cide-city-cy-cycle-dom-ectomy-ed-ee-eer-eme-en-en-ence-ency-ent-ent-eous-er-ergy-ern-ery-ese-esque-ess-etic-fare-ful-gon-gry-holic-hood-ia-iable-ial-ian-iant-iate-ible-ibly-ic-ical-ics-id-ier-ify-ile-illion-ious-ing-ion-ish-ism-ist-ite-itive-itude-ity-ium-ive-ization / isation-ize / ise-land-less-like-ling-ly-man-ment-meter-metry-mony-most-nesia-ness-ocracy-ography-ologist-ology-onomy-or-ory-ose-ous-phone-scope-ship-shire-sion-some-ster-t-th-tion-ty-uary-ulent-ward-wise-wright-yComfortableTriadBlockadeGaragePedagogyFocalAppraisalSexualityUrbanAnnoyanceVacancyRelevantAssistantLinearLiarWizardMilitaryDictionaryMonarchAnarchyFortunateCertificateConcentrateDecathlonConcentrationLucrativeLaboratoryOutboundSuicideAtrocityDiplomacyHydrocycleKingdomVasectomyBoredEmployeePrivateerMorphemeLeukemiaGoldenIndependenceFrequencyDifferentResidentCourteousWriterEnergySouthernMachineryChinesePicturesqueActressSympatheticWarfareHopefulPentagonAngryAlcoholicBrotherhoodManiaSociableSpecialItalianDefiantDeviateIncredibleResponsiblyHistoricHistoricalEconomicsCandidCashierClarifyTactileMillionAmbitiousPlayingActionFoolish, TallishEnglishBuddhismDentistSocialiteSensitiveAttitudeFormalityCalciumAggressiveOrganization/OrganisationIdolize/IdoliseFinlandCarelessChildlikeDucklingMonthlyFiremanGovernmentThermometerGeometryTestimonyInnermostPolynesiaKindness, DarknessDemocracyPhotographyArchaeologistBiologyAstronomyGovernorHistoryGlucoseNervousTelephoneTelescopeFriendshipOxfordshireDecisionAwesomeGangsterBurntGrowthIntroductionLoyaltyJanuaryFraudulentInwardClockwisePlaywrightSunnyCommon SuffixWord EndingExamples & List of Common SuffixesList of Suffixes
Nomos is a Greek term that can be translated as "law" or "custom." It refers to the social and cultural norms or laws that govern behavior within a community. In ancient Greek philosophy, nomos was contrasted with physis (nature) as a way to understand the principles that guide human society.