O
| Root | Meaning in English | Origin language | Etymology (root origin) | English examples |
|---|---|---|---|---|
| ob-, o-, oc-, of-, og-, op-, os- | against | Latin | ob | obstinate, obstreperous, occur, offend, omit, oppose, ostentatious |
| oct- | eight | Greek | ὀκτώ (oktō) | octagon, octahedron, octode |
| oct- | eight | Latin | octō | octangular, octennial, octovir |
| octav- | eighth | Latin | octāvus | octaval |
| octogen- | eighty each | Latin | octogeni | 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 (hodos) | anode, diode, odometer, pentode, tetrode, triode |
| od- | hate | Latin | odium | odious |
| odont- | tooth | Greek | ὀδούς, ὀδόντος (odous, odontos) | odontology |
| odor- | fragrant | Latin | odor | odorous |
| oeco- | house | Greek | οἶκος (oikos) | ecology |
| oed- | swollen | Greek | οἴδημα (oidēma) | oedema |
| oen- | wine | Greek | οἶνος (oinos) | oenology |
| oesophag- | gullet | Greek | οἰσοφάγος (oisophagos) | oesophagus |
| ogdo- | eighth | Greek | ὄγδοος (ogdoos) | ogdoad |
| -oid | like | Greek | -οειδής (-oeidēs) | asteroid, mucoid, organoid |
| ole- | oil | Latin | oleum | oleosity |
| olecran- | skull of elbow | Latin from Greek | ὠλέκρανον (ōlekranon) | olecranon |
| olig- | few | Greek | ὀλίγος (oligos) | oligarchy |
| oliv- | olive | Latin | oliva | olivaceous, olivary, olivette |
| -oma | cancer | Greek | -ωμα | melanoma |
| omas- | paunch | Latin | omasum | omasum |
| oment- | fat skin | Latin | omentum | omental |
| omin- | creepy | Latin | omen, ominis | abominable, ominous |
| omm- | eye | Greek | ὄμμα (omma) | ommatidium |
| omni- | all | Latin | omnis | omnipotence, omnivore |
| omo- | shoulder | Latin | ||
| omphal- | navel | Greek | ὀμφαλός (omphalos) | omphalectomy |
| oner- | burden | Latin | onus, oneris | exonerate, onerous |
| onom- | name | Greek | όνομα (onoma) | onomatopoeia |
| ont- | existing | Greek | ὄντος (ontos) | ontogeny, ontology |
| -onym | name | Greek | ὄνυμα (onuma) | antonym, pseudonym, synonym |
| oo- | egg | Greek | (oion) | oocyte |
| opac- | shady | Latin | opacus | opacity |
| oper- | work | Latin | opus, operis | inoperable, opera |
| opercul- | little cover | Latin | operculum | |
| ophi- | snake | Greek | ὄφις (ophis) | ophiophagy |
| ophthalm- | eye | Greek | ὀφθαλμός (ophthalmos) | ophthalmology |
| opisth- | behind | Greek | ὄπισθεν (opisthen) | opisthosoma, opsimath |
| opoter- | either | Greek | ὁπότερος (hopoteros) | |
| opt- | eye | Greek | ὀπτός (optos) | optical |
| opt- | choose | Latin | optare | adopt, optional |
| optim- | best | Latin | optimus | optimum |
| or- | mouth | Latin | os, oris | oral, orator |
| orb- | circle | Latin | orbis | orbit |
| orch- | testicle | Greek | ὄρχις (orchis) | orchid |
| ordin- | order | Latin | ōrdō, ordinis | ordinal, ordinary |
| organ- | organ, instrument, tool | Greek | ὄργανον (organon) | organism |
| ori-, ort- | eastern | Latin | oriri, ortus | orient |
| orn- | decorate | Latin | ōrnāre | adorn, ornament, ornate |
| ornith- | bird | Greek | ὄρνις (ornis, ornithos) | ornithology |
| orth- | straight | Greek | ὀρθός (orthos) | orthodontist, orthodoxy, orthosis |
| oscill- | swing | Latin | oscillum | oscillation |
| oss- | bone | Latin | os, ossis | ossification |
| osteo- | bone | Greek | ὀστοῦν (ostoun) | osteoporosis |
| osti- | entrance | Latin | ostium | ostiole |
| ostrac- | shell | Greek | ὄστρακον (ostrakon) | ostracism |
| ot- | ear | Greek | οὖς, ωτός (ous, ōtos) | otology |
| ov- | egg | Latin | ovum | oval, ovary, ovule |
| ovi- | sheep | Latin | ovis | ovine |
| oxy- | sharp, pointed | Greek | ὀξύς (oxus) | oxygen, oxymoron |
Read more about this topic: List Of Greek And Latin Roots In English