Root Meaning in English Origin language Etymology (root origin) English examples ob- , o- , oc- , of- , og- , op- , os- [ 1] against Latin ob obduracy, obdurate, obduration, obfuscate, oblique, obliquity, obstinate, obstreperous, occur, offend, omit, oppose, ostensible, ostentatious obel- [ 2] spit , nail Greek ὀβελός (obelós ὀβελίσκος (obelískos metobelus, obelisk , obelism , obelus obol- [ 3] nail Greek ὀβολός, ὀβολοῦ (obolós, oboloû obol , obolus ocean- [ 4] river, stream Greek ὠκεανός (ōkeanós Oceania, oceanic ochl- [ 5] crowd, mob Greek ὄχλος, ὄχλου (ókhlos, ókhlou enochlophobia, ochlocracy , ochlophobia oct- [ 6] eight Greek ὀκτώ (oktṓ ὀκτάς oktás ὀκτάκις oktákis hemi-octahedron , octad, octadic, octagon , octahedron , octameter , octode oct- eight Latin octō octangular, octennial, octovir octav- eighth Latin octāvus octaval octogen- eighty each Latin octogeni octogenarian, octogenary octogesim- eightieth Latin octogesimus octogesimal octon- eight each Latin octoni octonary ocul- eye Latin oculus , oculare ocular, oculus , ullage od- path, way Greek ὁδός (hodós anode , diode , odometer , parodos , pentode , tetrode , triode odi- hate Latin odium odious odont- [ 7] tooth Greek ὀδούς, ὀδόντος (odoús, odóntos anodontia, conodont, cynodont , dicynodont, dysodontiasis, macrodontia, mastodon , odontoid, odontology , odontophore , orthodontics , orthodontist, pedodontics , periodontal, smilodon, Thrinaxodon , Zanclodon odor- fragrant Latin odor malodorous, odoriferous, odorous odyn- [ 8] pain Greek ὀδύνη (odúnē allodynia , anodyne , glossodynia, mastodynia , pleurodynia oec- [ 9] house Greek ϝοῖκος woîkos οἶκος (oîkos andromonecy, archdiocese, autoecious , autoecism , dioecious , dioecy , ecesis, ecologist, ecology , economics , economist, economize, economy , ecoregion , ecosystem, ecumenic, ecumenism , gynomonoecy, heteroecious , heteroecism , heteroecy, homoecious, monoecious , monoecy , oecology , oeconomus , oecumenic, oikology, oikophobia , palaeoecology, paleoecology , parish , paroecious, perioeci , trioecious oed- , ed- swell, swollen Greek οἶδος oîdos οἰδεῖν (oideîn οἴδημα, οἴδηματος (oídēma, oídēmatos angioedema, edema , edematous, oedema , oedematous oen- [ 10] wine Greek ϝοῖνος woînos οἶνος (oînos enology, oenochoe , oenologist, oenology , oenophile , oenophilia , oinochoe oesophag- [ 11] gullet Greek οἰσοφάγος (oisophágos oesophagectomy, oesophagitis, oesophagus oestr- [ 12] gadfly, sting Greek οἶστρος (oîstros οἰστράω, οἴστρησις οἴστρημα anestrous, anestrus, anoestrus, estrogen, estrogenic, estrus, oestrone , oestrus ogdo- [ 13] eighth Greek ὄγδοος (ógdoos ὀγδοάς, ὀγδοάδος (ogdoás, ogdoádos ogdoad -oid like Greek -οειδής (-oeidēs) asteroid, mucoid, organoid ole- oil Latin oleum oleosity olecran- [ 14] skull of elbow Latin from Greek ὠλέκρανον (ōlékranon olecranon olig- [ 15] few Greek ὀλίγος (olígos oligarchy , Oligocene, oligopoly, oligosaccharide, oligotrophic oliv- olive Latin oliva olivaceous, olivary, olivette om- [ 16] raw Greek ὠμός (ōmós ὠμότης ōmótēs omophagia, Omophagus om- [ 17] shoulder Greek ὦμος (ômos ὠμία ōmía acromion , omohyoid , omophorion -oma morbid growth, tumor Greek -ωμα melanoma omas- paunch Latin omasum abomasum, omasum ombr- [ 18] rain Greek ὄμβρος (ómbros ombrogenous, ombrology, ombrometer , Ombrophila , ombrophilous, ombrophobe , ombrotrophic oment- fat skin Latin omentum omental omin- creepy Latin omen , ominis abominable, ominous ommat- eye Greek ὁράω, ὦμμαι ὄμμα, ὄμματος (ómma, ómmatos ommatidium , ommatophore omni- all Latin omnis omnipotence , omnipresent, omniscient, omnivore omphal- [ 19] navel Greek ὀμφαλός (omphalós omphalectomy, omphalic, omphalopagus, omphalophobia, paromphalocele on- [ 20] ass Greek ὄνος (ónos ὀνίσκος onískos Oniscidea, Oniscomorpha onc- [ 21] barb , hook Greek ὄγκος ὄγκινος (ónkinos Oncinocalyx , Oncorhynchus onc- [ 22] (ΕΓΚ [ 23] )bulk Greek ἐνεγκεῖν ὄγκος (ónkos ὀγκόω, ὀγκωτός, ὄγκωσις ὄγκωμα oncocyte , oncocytoma , oncogenesis , oncologist, oncology oneir- [ 24] dream Greek ὄνειρος (óneiros ὀνειρώσσω ὀνείρωξις oneírōxis oneiric , oneirism, oneirocritic, Oneirocritica , Oneirodidae , oneirogen , oneirogenic , Oneiroi , oneiroid , oneirology , oneiromancy , oneironaut, oneironautics , oneirophobia , oneirophrenia , oneiroscopy oner- burden, load Latin onus , oneris exonerate, exoneration, onerous, onus oni- [ 25] price Greek ὦνος (ônos ὤνιος ṓnios oniochalasia , oniomania , oniomaniac onomat- [ 26] name Greek ὄνομα, ὀνόματος (ónoma, onómatos ὀνομάζω ὀνομαστικός onomastikós antonomasia , onomasiology , onomastic, onomasticon, onomastics , onomasty , onomatology , onomatophore , onomatopoeia ont- being , existence Greek ὄντος, ὀντότης (óntos, ontótēs οὐσία (ousía dysontogenesis, homoiousia, homoousia, monoousious, ontogenesis, ontogenetic, ontogeny , ontology , ousia , parousia onych- [ 27] claw Greek ὄνυξ, ὄνυχος (ónux, ónukhos ὀνύχιον onúkhion ὀνύχινος ὀνυχίζω hapalonychia , Mesonychia , onychectomy , onycholysis , onychomancy , onychomycosis , onychophagia , onychophagy , onychorrhexis , onyx , paronychia , sardonyx onym- [ 28] name Greek ὄνυμα (ónuma acronym , allonym , anonymous, antonym , autonym, caconym, cryptonym, eponym , eponymous, eponymy , euonym, homonym , hyperonym , hyponym , hyponymy, meronym, meronymy , metonym, metonymy , metronymic, paronym, paronymous, pseudonym , pseudonymous , synonym , synonymous , synonymy , tautonym , tautonymous, tautonymy , troponym , troponymy , xenonym , xenonymy oo- [ 29] egg Greek ᾠόν (ōión bottarga , dioon , epoophoron , oidioid, oidium , ooblast, oocyst , oocyte , oocytogenesis, oogamete, oogamous, oogamy , oogenesis , oogonium , ooid , oolite , oolith , oology , oomancy , oophagy , oophorectomy , oophoron, ootheca , ootid , ootidogenesis , paroophoron op- [ 30] hole Greek ὀπή (opḗ ὀπαῖον (opaîon metope , opaion opac- shady Latin opacus opacity , opacus , opaque oper- work Latin opus , operis cooperate, inoperable, opera , operate, opus oper- cover Latin operire , operculum interoperculum, kerchief , opercular, operculiform, operculum ophi- [ 31] snake Greek ὄφις, ὄφεως (óphis, ópheōs Brachyurophis , ophicephalous, Ophicephalus, Ophiceras, Ophiclinus , ophidiophobia , ophiolite, ophiologist, ophiology, ophiophagous, Ophiophagus ophiophagy , ophiophobia , Ophisaurus , Ophisops , ophitic ophthalm- [ 32] eye Greek ὀφθαλμός (ophthalmós exophthalmic , exophthalmos , microphthalmia , ophthalmia , ophthalmic, ophthalmologic, ophthalmologist , ophthalmology , ophthalmoparesis , ophthalmoplegia , parophthalmia, xerophthalmia opisth- [ 33] behind Greek ὄπισθεν (ópisthen ὀπίσθιος anopisthograph, opisthion , opisthobranch, opisthodomos , opisthoglyphous, opisthognathous, opisthograph , opisthokont , opisthosoma , opsimath , opsimathy ops- , opt- (ΟΠ) eye Greek ὄψεσθαι (ópsesthai ὀπτός optós ὀπτικός optikós ὄψις (ópsis amblyopia , anopia, autopsy , biopsy , catadioptrics , catoptrics , catoptromancy , catoptrophobia , cyclops , diopter, dioptre , dioptrics , diplopia , eisoptrophobia, emmetropia, hemianopsia, myopia, opsoclonus , optic, optokinetic , panopticon , pleoptics, synopsis, synoptic, tritanopia opsi- [ 34] late Greek ὀψέ (opsé ὄψιος opsimath opson- [ 35] cook, prepare for eating Greek ὀψωνεῖν (opsōneîn opsōnia ) opsonin , opsonoid opt- choose Latin optare adopt, adoptee, adoption, adoptive, co-option , coopt, cooptation, nonoptional, opt, optation, optative , option, optional, optionality optim- best Latin optimus optimal, optimum or- , oro- [ 36] mountain Greek ὄρος, ὄρεος (óros, óreos ὀρειάς Oread , orogenesis , orogenic, orogeny , orographic, orography, oronym or- mouth Latin os (genitive oris adosculation, inosculate, inosculation , interosculate, intraoral, oral, orifice, osculant , osculum , peroral ora- pray, plead Latin orare "to pray, plead"adore, adoration , exorable, inexorable, oracle, orate, oration, orator , oratorio , oratory, orison, perorate, peroration, perorator orb- circle Latin orbis orbit orch- [ 37] testicle Greek ὄρχις (órkhis ὀρχίδιον orkhídion anorchia , cryptorchidism , monorchism , orchid , orchiectomy , orchiopexy , Orchis , polyorchidism orches- [ 38] dance Greek ὀρχεῖσθαι (orkheîsthai orchestra ordin- order Latin ōrdō , ordinis coordinal, coordinate, coordination, coordinator, disorder, extraordinaire, extraordinary, grandorder , incoordinate, incoordination, infraorder , inordinate, inordination, insubordinate, insubordination , magnorder , mirorder , ordain, ordainment, order, ordinal , ordinance , ordinand, ordinariate, ordinary , ordinate , ordination , ordinative, ordnance, ornery, parvorder , preordain, preorder , preordination, quasiorder , reordain, reorder, reordination , suborder , subordinary , subordinate, subordination, superordain, superorder , superordinate, superordination oreg- [ 39] reach Greek ὀρέγειν (orégein ὀρεκτός orektós ὀρεκτικός orektikós ὄρεξις órexis ὄρεγμα óregma anorectic, anorexia, dysorexia, orectic, orexin , parorexia org- work Greek ὄργια órgia orgasm organ- organ, instrument, tool Greek ὄργανον (órganon organic, organism , organogenesis ori- , ort- rise Latin oriri , ortus aboriginal, abort, abortifacient, abortion, abortive, disorient, disorientation, orient, oriental, Orientalia, orientate, orientation, orientational, orientative , origin, original, originality, originate, origination, originator, reorient, reorientation orn- decorate Latin ōrnāre adorn, adornment, ornament, ornamental, ornamentation, ornate, ornative , ornature, suborn, subornation ornith- [ 40] bird Greek ὄρνις, ὄρνιθος (órnis, órnithos Avernus , ornithology , ornithomancy , ornithorhynchus, ornithosis orphan- [ 41] Greek ὀρφανός (orphanós ὀρφανότης orphan orth- [ 42] straight Greek ὀρθός (orthós ὀρθότης orthocenter, orthocentric , orthodontia, orthodontic , orthodontist , orthodox, orthodoxy , orthographic, ortholog, orthologous, orthonym , orthopedic , orthoscope, orthosis , orthostat , orthostyle, orthotic oryz- [ 43] rice Greek ὄρυζα (óruza ὀρύζιον Oryza , Oryzomys , rice, risotto oscill- swing Latin oscillum oscillate, oscillation , oscillator, oscillatory osm- [ 44] odor Greek ὀσμή (osmḗ ὄσμησις anosmia , anosmic, cacosmia, coprosmia, dysosmia , dysosmic, euosmia, hyperosmia , hyperosmic, hyposmia , hyposmic, osmium , osmolagnia , osmophobia , osphresiolagnia, parosmia , phantosmia , troposmia osm- [ 45] push, thrust Greek ὠσμός (ōsmós osmometry, osmosis , osmostat , osmotic oss- bone Latin os , ossis exossation, interosseous, ossature, osselet, osseocartilaginous, osseointegration , osseous, ossicle, ossicular, ossiferous, ossification , ossifrage, ossify, ossuary oste- [ 46] bone Greek ὀστέον, ὀστέου (ostéon, ostéou ὀστοῦν, ὀστοῦ (ostoûn, ostoû dysostosis , endosteum , exostosis , hyperostosis , monostotic, Osteichthyes , osteoarthritis , osteoblast , osteochondritis , osteochondrosis , osteoclast , osteogenic , osteogenesis , osteoid , osteology , osteolysis , osteoma , osteomalacia , osteonecrosis , osteopathy , osteopenia , osteoporosis , osteosarcoma , osteosis, osteothrombosis, osteotome , osteotomy , periosteum, synostosis osti- entrance Latin ostium ostiary , ostiolar, ostiole , ostium ostrac- shell Greek ὄστρειον óstreion ὀστρακίζω ostrakízō ὄστρακον óstrakon Entomostraca , Leptostraca , Malacostraca , ostracism , ostracize, ostracod, ostracoderm , ostracon , periostracum ostre- [ 47] oyster Greek ὄστρεον ostreophagist, oyster ot- [ 48] ear Greek οὖς, ὠτός (oûs, ōtós anotia , Aotus, microtia , Myosotis , otalgia , otic, otitis, otocephaly , otocleisis, otoconium, otocyst, otodynia, otolith , otology , otopathy, otophyma , otoplasty , otorhinology, otorrhea, otosclerosis , otoscope , otoscopy, ototomy, parotic, parotid , periotic, synotia ov- egg Latin ovum obovate, oval , ovarian, ovariole , ovary, ovate, ovicapsule, ovicidal, ovicide, oviduct , oviferous, oviform, oviposition , ovipositor , ovolo , ovular, ovulation , ovulatory , ovule , ovum , pluriovulate ovi- sheep Latin ovis ovile, ovine oxy- [ 49] sharp, pointed Greek ὀξύς (oxús anoxia, anoxic, dioxide, hypoxia, monoxide, oxide, oxyanion , oxygen , oxyhalide , oxymoron , oxyntic, oxytone , paroxysm , pentoxide, polyoxide, tetraoxygen , tetroxide, trioxide oz- [ 50] smell Greek ὄζειν (ózein ὄζων ózōn ὄζη ozocerite , ozone , ozopore