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MedTerms Medical Dictionary A-Z List - O: Detailed Datasheet
Medically reviewed by Min Clinic Staff | Updated: January 2026
Oa-OcOd-OmOn-OqOr-OrOs-OsOt-OwOx-Oz
OOa-Oc
- OAE
- Oat cell cancer
- Oath of Maimonides
- OB
- OB/GYN
- Obese
- Obesity
- Obesity, endogenous
- Obesity, exogenous
- Obesity, gynecoid
- Obesity-related disease
- Objective
- OBS
- Observer variation
- Obsessive-compulsive disorder
- Obsessive-compulsive personality disorder
- Obstetrical forceps
- Obstetrician
- Obstetrician/gynecologist
- Obstetrics
- Obstruction
- Obstruction, airway
- Obstruction, intestinal
- Obstructive sleep apnea
- Obtund
- Obtunded
- Obverse
- Occam's razor
- Occipital
- Occipital bone
- Occipital hematoma
- Occiput
- Occlude
- Occlusion
- Occult
- Occult stool blood test
- Occupational disease
- Occupational medicine
- Occupational Safety and Health Administration
- Occupational Safety and Health, Nat'l Institut for
- Occupational therapist
- OCD
- Ocean itch
- OCG
- Ochronosis
- OCP
- OCPD
- Octogenarian
- Ocular
- Ocular conjunctiva
- Ocular Cryotherapy
- Ocular histoplasmosis syndrome
- Ocular melanoma
- Ocular migraine
- Ocular prosthesis
- Oculo-auriculo-vertebral spectrum
- Oculoauriculovertebral dysplasia
- Oculocraniosomatic syndrome
- Oculocutaneous albinism
- Oculodentodigital dysplasia
- Oculomotor nerve
- Oculoplastics
OOd-Om
- OD (lens prescription)
- ODD syndrome
- Odynophagia
- Oesophagus
- Off-label use
- Off-pump
- Off-pump CABG
- Off-pump surgery
- Office of Human Research Protections (OHRP)
- Offspring
- OGG1
- OHRP
- Oil, tropical
- Ointment
- Okihiro syndrome
- OKT3
- Olecranon
- Olefaction
- Olefactory
- Olfaction
- Olfactory
- Olfactory apparatus
- Olfactory bulb
- Olfactory disorder
- Olfactory nerve
- Olfactory system
- Oligo- (prefix)
- Oligoarthritis
- Oligoastrocytoma
- Oligodactyly
- Oligodendrocyte
- Oligodendroglioma
- Oligohydramnios
- Oligomenorrhea
- Oligonucleotide
- Oligonucleotide probe
- Oligopeptide
- Oligospermia
- Oliguria
- Oliva
- Olivae
- Olivary
- Olive
- Olive oil diet
- Oliver Wendell Holmes, Sr.
- Olivo-
- Olivopontocerebellar
- Olivopontocerebellar atrophy
- Ollier disease
- oma
- Omega-3 fatty acids
- Omentectomy
- Omentum
- Ommaya reservoir
- Omniscience
- Omphalo-
- Omphalocele
- Omphalos
- OMS
- OMS (World Health Organization)
OOn-Oq
- On call
- Onchocerciasis
- Oncogene
- Oncogene ErbB
- Oncologist
- Oncology
- Ondine's curse
- Oneiric
- Oneirophrenia
- Oneself, fear of
- Onset
- Onycho- (prefix)
- Onychocryptosis
- Onychodystrophy
- Onychogryphosis
- Onychogryposis
- Onycholysis
- Onychomycosis
- Onychomycosis, proximal white subungual
- Onychoosteodysplasia
- Oocyte
- Oogenesis
- Oogonium
- Oophorectomy
- Oophoritis
- OPCA
- Open charting
- Open cholecystectomy
- Open fracture
- Open heart surgery
- Open reading frame
- Open wound
- Open-angle glaucoma
- Open-label
- Open-label trial
- Opening, vaginal
- Operating room
- Operation
- Operation, Blalock-Taussig
- Operation, Glenn
- Operation, Macewen
- Operon
- Ophthalmia
- Ophthalmic
- Ophthalmic artery
- Ophthalmic migraine
- Ophthalmic veins
- Ophthalmitis
- Ophthalmologist
- Ophthalmology
- Ophthalmopathy
- Ophthalmoplegia with myopathy
- Ophthalmoplegia with ragged-red fibers
- Ophthalmoplegia-plus syndrome
- Ophthalmoscope
- Ophthalmoscopy
- Opiate
- Opiate agonist maintenance
- Opioid
- Opisthotonos
- Opium
- Opportunistic condition
- Opportunistic infection
- Opportunistic microorganism
- Optic
- Optic cup
- Optic disc
- Optic glioma
- Optic nerve
- Optic nerve head
- Optic nerve pathways
- Optic Nerve Sheath Fenestration
- Optic neuroma
- Optician
- Optometrist
- OPV
OOr-Or
- OR (abbreviation)
- Oral
- Oral allergy syndrome
- Oral aversion
- Oral cancer
- Oral candidiasis
- Oral cholecystogram
- Oral contraceptive
- Oral contraceptive, combined
- Oral glucose tolerance test
- Oral moniliasis
- Oral rehydration salts
- Oral rehydration therapy
- Oral surgeon
- Oral-motor
- Orbit
- Orbital
- Orbital fracture
- Orbital ridge
- Orchiectomy
- Orchiopexy
- Orchitis
- Ordre des Medecins
- ORF
- Organ
- Organ failure
- Organ of hearing
- Organic
- Organic brain syndrome
- Organic dust toxic syndrome
- Organic toxic dust syndrome OTDS
- Organisation Mondiale de la Sante
- Organotherapy
- Organs of reproduction, female
- Organs of reproduction, male
- Orgasm
- Orgasmic disorder
- Orgasmic dysfunction
- Orgasmic inhibition
- Oriental lung fluke
- Oriental medicine (traditional)
- Orientation, anatomic terms of
- Orifice
- Ornithine
- Ornithine transcarbamylase (OTC) deficiency
- Ornithophobia
- Oromandibular dystonia
- Oropharynx
- Orphan disease
- Orphan drug
- ORS
- Ortho- (prefix)
- Orthodontic treatment (dental braces)
- Orthodontics
- Ortholog
- Orthologous gene
- Orthomolecular medicine
- Orthopaedics
- Orthopaedist
- Orthopedics
- Orthopedist
- Orthopnea
- Orthopod
- Orthopox
- Orthorexia nervosa
- Orthoscopic
- Orthosis, thoracolumbosacral (TLSO)
- Orthostatic hypotension
- Orthotic
- Oryzomys palustris
OOs-Os
- Os
- OS (lens prescription)
- Os calcis
- Os sacrum
- OSA (obstructive sleep apnea)
- Oscillating vision
- Oscillopsia
- Oscitation
- Osgood-Schlatter disease
- OSHA
- Osler's nodes
- Osler, Sir William
- Osler-Rendu-Weber syndrome
- Osmolar
- Osmolarity
- Osmolarity, plasma
- Osmole
- Osseous
- Ossicle
- Ossification
- Ossify
- Osteitis
- Osteitis deformans
- Osteitis fibrosa cystica
- Osteo- (prefix)
- Osteoarthritis
- Osteoarthropathy
- Osteoblast
- Osteoblastoma
- Osteochondritis dissecans
- Osteochondroma
- Osteochondromatosis
- Osteochondromatosis, synovial
- Osteochondrosis
- Osteoclasia
- Osteoclasis
- Osteoclast
- Osteoclastoma
- Osteocyte
- Osteodystrophy
- Osteodystrophy, renal
- Osteogenesis
- Osteogenesis imperfecta
- Osteogenesis imperfecta congenita
- Osteogenesis imperfecta tarda
- Osteogenesis imperfecta type 1
- Osteogenesis imperfecta type 2
- Osteogenesis imperfecta with blue sclerae
- Osteogenesis, electrically stimulated
- Osteoid osteoma
- Osteology
- Osteolytic
- Osteolytic lesion
- Osteomalacia
- Osteomyelitis
- Osteonecrosis
- Osteopath
- Osteopathy
- Osteopenia
- Osteopetrosis
- Osteoporosis
- Osteosarcoma
- Osteosynthesis
- Osteotomy
- Osteotomy, block
- Osteotomy, cuneiform
- Osteotomy, displacement
- Ostomy
- Oswald Theodore Avery
OOt-Ow
- Ot-
- Otalgia
- OTC (over-the-counter)
- Othello psychosis
- Othello syndrome
- Otic barotrauma
- Otitis
- Otitis externa
- Otitis interna
- Otitis media
- Otitis media, acute
- Oto-
- Otoacoustic emission test
- Otolaryngologist
- Otolaryngology
- Otology
- Otopharyngeal tube
- Otoplasty
- Otosclerosis
- Otoscope
- Ototoxicity
- Ounce
- Outer ear
- Outlet
- Outlet, gastric
- Outpatient
- Output, cardiac
- Ova
- Ovarian
- Ovarian cancer
- Ovarian cancer gene BRCA2
- Ovarian cancer test CA 125
- Ovarian cyst
- Ovarian pregnancy
- Ovarian remnant syndrome
- Ovarian teratoma
- Ovariectomy
- Ovary
- Ovary cyst, follicular
- Ovary, dermoid cyst of the
- Ovary, polycystic
- Over-the-counter (OTC) drug
- Overactive bladder
- Overbreathing
- Overgrowth
- Overgrowth syndrome
- Overload, iron
- Overweight
- Ovulation
- Ovulatory
- Ovum
OOx-Oz
- Oxter
- Oxy
- Oxycodone
- OxyContin
- Oxygen
- Oxygen mask
- Oxygen tent
- Oxygenate
- Oxygenating
- Oxygenation
- Oxyhemoglobin
- Oxymetholone
- Oxytocin
- Oxyuris
- oz.
- Ozone