List Of Nouns Starting With “O”

Explore the world of nouns starting with the letter O! This comprehensive list contains 1,821 nouns beginning with the letter O, arranged alphabetically. The nouns range from everyday words to more obscure terms, with examples such as ‘overoxidization’ (the process of oxidizing too much), ‘oligocythemia’ (a decrease in the number of red blood cells), ‘overcriticism’ (excessive criticism) and ‘organist’ (a musician who plays the organ). Other nouns include ‘orthros’ (a religious office in Eastern Orthodox churches).

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With so many words to explore, this list of nouns starting with O is sure to help you find the perfect word for your needs. Whether you’re a student, a teacher, a writer or just someone who loves language, this list has something for everyone. Start exploring today and see what new words you can discover!

The words arranged in the lists below are in alphabetical order, from left to right and down.





List Of 3-Letter Nouns That Start With “o”

oaf
oak
oat
oba
obb
obe
obi
obj
obs
oca
oct
ode
ohm
oik
oka
ola
ole
olm
ona
oni
ont
oof
opa
opp
ops
ora
orc
ore
osi
otc
oud
ova
owl

List Of 4-Letter Nouns That Start With “o”

Oahu
oaks
oast
oath
oban
obdt
obit
oboe
odel
Oder
odin
odor
odyl
ofay
Offa
ogam
ogee
ogpu
ogre
ohio
ohms
Oise
okie
okra
okta
olaf
olds
olea
oleg
olga
olio
olla
olpe
oman
omar
omer
omni
Omsk
oner
onus
onyx
Oona
oose
opah
opal
opec
opus
Oran
orca
orch
ordn
ordo
orfe
Orff
orgy
orig
orle
orlo
orly
orna
Orne
orth
oryx
oslo
ossa
otis
otto
otus
Oudh
Ouse
ouzo
oven
ovid
ovum
owen
oxen
Oxus
oyer
ozan
Ozzy
oakum
oasis
oater
Oates
obeah
obole
Occam
occas
ocean
ocker
ocrea
octad
octet
odell
odeum
odium
odour
offal
Ogdon
ogham
ogive
ohare
oiler
oisin
okapi
oldie
olein
oleum
oliva
olive
ollie
ology
olson
Olwen
Omagh
omaha
omber
ombre
omega
oncer
onion
onker
onlap
onset
oomph
ootid
opera
ophir
opium
opsin
orach
oracy
orang
Orcus
Orczy
oread
Orfeo
organ
oribi
oriel
orion
oriya
orlon
orlop
ormer
ornis
orris
orson
Orton
osage
osaka
oscar
osier
oskar
Osric
osset
ostia
othin
ottar
otter
Otway
ouija
Oujda
ounce
ouphe
ousel
ouzel
ovary
ovolo
ovule
Owens
owlet
owner
oxbow
oxeye
oxide
oxime
oxlip
oxter
ozark
ozone
Ozzie

List Of 6-Letter Nouns That Start With “o”

Oakham
Oakley
Oaxaca
obeche
obelia
obelus
oberon
obeyer
oblast
obolus
obrien
obstet
ocelot
ochrea
Ockham
octane
octans
octant
octave
octavo
octroi
oculus
oddity
odelet
Odense
odessa
Odette
oedema
oenone
oeuvre
Offaly
office
offing
offlap
Ogaden
ogdoad
ohmage
oidium
oilcan
oilcup
oilman
ojibwa
okoume
Oldham
oleate
olefin
oliver
olives
olivia
omasum
omelet
ommiad
onager
oncost
ondine
onding
oneida
oneill
onions
onrush
onyxis
oocyte
oogamy
oolite
oolith
oology
oolong
oomiak
oompah
Oonagh
opaion
opcode
opener
operon
ophion
ophite
oporto
optics
optime
option
orache
oracle
orange
orator
orcein
orchid
orchil
orchis
ordeal
ordure
oregon
orexis
orfray
organa
orgasm
orgeat
orient
origan
Origen
origin
orihon
oriole
orison
Orissa
orkhon
ormazd
ormolu
ormond
ornith
oroide
orpine
orrery
Orsini
Orsino
ortrud
orwell
Osbert
osiris
osmics
osmium
osmond
osmund
osprey
ossein
ossian
ostend
ostium
ostler
ostyak
oswald
oswego
otello
otitis
ottava
ottawa
ourari
ouster
outage
outing
outlaw
outlet
output
outset
ovambo
Oviedo
ovisac
owelty
oxalis
oxcart
oxford
oxgang
oxhide
oxtail
oxygen
oyelet
Ozalid

List Of 7-Letter Nouns That Start With “o”

oakland
oakmoss
oarfish
oarlock
oarsman
oatcake
oatmeal
obadiah
obelisk
obesity
obligee
obliger
obligor
obloquy
ocarina
occiput
oceania
oceanid
oceanog
oceanus
ocellus
oconnor
octagon
octavia
october
octopus
oculist
ocypete
oddment
oddness
oddside
odinism
odinist
odylism
odylist
odyssey
oedipus
oenomel
oersted
oestrin
oestrus
offence
offense
offerer
offeror
offtake
oilbird
oilfish
oilseed
oilskin
Okayama
okinawa
oldster
oldwife
olefine
olivier
olivine
oloroso
olympia
olympus
Omayyad
omentum
omicron
onanism
onanist
Onassis
oncosis
one-off
one-two
oneness
ontario
onychia
oophore
oophyte
oosperm
oospore
ootheca
opacity
opalina
opening
operand
opercle
ophelia
opinion
opossum
opposer
opsonin
opuntia
oquassa
orarion
orarium
oration
oratory
oratrix
orbital
orchard
orcinol
oregano
orestes
organdy
organon
organum
organza
orifice
origami
Orinoco
orlando
orleans
Ormandy
orogeny
orpheus
orphism
orphrey
orthros
ortolan
orvieto
orville
Osborne
osculum
osmosis
osmunda
osselet
ossicle
ossuary
osteoma
ostiary
ostiole
ostmark
ostosis
ostrich
otalgia
othello
otocyst
otolith
otology
Otranto
Ottilie
ouabain
outcity
outcome
outfall
outflow
outflux
outhaul
outlier
outlook
outness
outpath
outport
outpost
outrush
outsert
outshot
outsole
outturn
outwash
ovality
ovarium
ovation
overfee
oviduct
owenism
owenist
owenite
oxalate
oxazine
oxheart
oxidant
oxidase
oxyacid
oxydase
oxysalt
ozonide

List Of 8-Letter Nouns That Start With “o”

obeahism
Oberland
obituary
objector
oblation
oblivion
observer
obsidian
obsolesc
obstacle
obtruder
occamism
occamist
occamite
occident
occulter
occupant
occupier
ochlesis
ocotillo
octangle
octarchy
octaroon
octavian
octavius
octofoil
octoroon
odometer
odometry
odysseus
oecology
oeillade
oenology
oenomaus
oestriol
oestrone
offender
offering
offshoot
offsider
ogallala
ohmmeter
oilcloth
oilfield
oiliness
oilstone
oinochoe
ointment
Oistrakh
oiticica
Okavango
oklahoma
oleander
oleaster
olibanum
oligarch
oliguria
oliphant
olivette
olympiad
olynthus
omadhaun
Omdurman
omelette
omission
omnivore
omphalos
oncology
ondogram
one-step
onlooker
onondaga
ontogeny
ontology
oogonium
oolachan
oosphere
Oostende
openwork
operator
operetta
ophthalm
opinicus
opiumism
oppugner
opsimath
optician
opticist
optimise
optimism
optimist
optionee
optotype
opulence
orangery
oratorio
orbitale
orchitis
ordainer
ordinand
ordnance
oreshoot
oresteia
organdie
organism
organist
ornithol
orometer
orometry
orpiment
orseille
orthicon
orthoepy
osnaburg
osophone
ossifier
osteitis
ostinato
ostracod
ostracon
otoscope
otoscopy
ottinger
outbreak
outburst
outclerk
outcurve
outfield
outgroup
outguard
outhouse
outlawry
outliver
outpupil
outrance
outrider
outsider
outskirt
outswing
ovalness
ovaritis
ovenbird
ovenware
ovenwood
overbite
overboot
overcare
overcoat
overcoil
overdyer
overfall
overflap
overfold
overkill
overline
overlord
overmast
overness
overplus
overseer
overshoe
oversoul
overspin
overtone
overview
overword
Oxbridge
oxidizer
oximeter
oximetry
oxpecker
oxtongue
oxymoron
oxytocia
oxytocin
ozonizer
obedience
obeisance
objection
obligator
obliquity
oblongata
obreption
obscenity
obscurity
obsession
obstinacy
obstipant
obtundity
obturator
obversion
occlusion
occupancy
oceanside
ochlocrat
octachord
octameter
octateuch
octillion
octobrist
ocularist
odalisque
oddfellow
odelsting
oestrogen
Offenbach
offertory
officiant
offspring
oftenness
Ogbomosho
old-timer
oldenburg
olecranon
oleograph
oleoresin
olfaction
oligarchy
oligopoly
olivenite
ombudsman
omnigraph
omnirange
omophagia
once-over
ondograph
ondometer
ondoscope
one-acter
onerosity
oniomania
onionskin
onslaught
oogenesis
opacifier
operation
operculum
ophiology
opodeldoc
opponency
oppressor
optometer
optometry
orangeade
orangeism
orangeist
orangeman
orangutan
oratorian
orchestra
orchotomy
ordinance
organelle
organizer
organzine
oriflamme
origenism
origenist
orleanism
orleanist
ornithine
orography
orologist
orphanage
orpharion
orpington
orrisroot
ortanique
orthodoxy
orthopnea
orthopter
orthostat
oscitance
oscitancy
osmometer
osmometry
ossifrage
ostectomy
ostensory
osteology
osteopath
osteotome
osteotomy
ostracise
ostracism
ostringer
ostrogoth
otherness
otologist
otoplasty
Otterburn
ottrelite
oubliette
outbidder
outerness
outerwear
outfitter
outgrowth
outlander
outoffice
outparish
outporter
outrigger
outrunner
outsentry
outworker
overbreak
overcheck
overcomer
overdraft
overeater
overrider
overruler
overshirt
oversight
overskirt
oversness
overstand
overtread
overtrick
oviparity
ovotestis
ownership
oxidation
oxydation
oxygenate
oystering
oysterman
ozocerite

List Of 10-Letter Nouns That Start With “o”

oast-house
Oberhausen
objurgator
obligation
oblongness
obrogation
obsequence
observance
obstetrics
obstructer
obstructor
obturation
obvolution
occultness
occupation
occurrence
oceanarium
oceanfront
oceanicity
oceanology
ocellation
ochlocracy
octahedron
octastylos
octodecimo
odd-jobman
odiousness
odontalgia
odontiasis
odontogeny
odontolite
odontology
oenologist
oesophagus
oestradiol
officiator
offishness
oireachtas
oktastylos
oleography
oligoclase
oligopsony
ombrellino
ommatidium
omophagist
omophorion
oniomaniac
onomastics
ontogenist
ontologism
ontologist
oophoritis
opacimeter
opaqueness
operettist
ophicleide
ophiolater
ophiolatry
ophthalmia
opisthenar
oppilation
opposition
oppression
opprobrium
orang-utan
orange-tip
orangewood
oratorship
orchardist
orchardman
orchectomy
ordainment
ordination
ordonnance
organicist
organicity
organology
originator
ornateness
orneriness
ornithopod
ornithosis
orographic
orotundity
orphanhood
orthoclase
orthopraxy
orthoptics
orthoscope
oscillator
oscularity
osculation
osmaterium
osmeterium
osmidrosis
osmiridium
osteectomy
osteoblast
osteoclast
osteologer
osteopathy
osteophyte
ostracizer
ouananiche
outdweller
outfielder
outflanker
outkitchen
outpatient
outpouring
outswinger
ovariotomy
overaction
overbearer
overblouse
overdesire
overdrawer
overeffort
overflight
overgrowth
overhearer
overidness
overlaness
overliking
overlooker
overmantel
overmatter
overnicety
overplenty
overraness
oversetter
oversleeve
oversurety
overtalker
overthrust
overwealth
overweener
ovipositor
owlishness
oxidimetry
oxybenzene
oxycephaly
oxygenator
oxygenizer
oxyneurine
ozonolysis

List Of 11-Letter Nouns That Start With “o”

obfuscation
objectivism
objectivity
objurgation
obligedness
obscureness
obsecration
observation
observatory
obstipation
obstruction
obtestation
obumbration
obviousness
occultation
ochlophobia
octahedrite
odontoblast
odontograph
odontophore
off-licence
officialdom
officialese
officialism
officiation
offscouring
oillessness
oligochaeta
oligotrophy
ominousness
ommatophore
omnibearing
omnificence
omnipotence
omniscience
omphalocele
one-nighter
oneiromancy
onerousness
onomatology
openairness
operability
operativity
operoseness
ophiologist
ophthalmiac
Oppenheimer
opportunism
opportunity
optionality
optometrist
oracularity
orbicularis
orchestrion
orchidology
orchidotomy
orchiectomy
ordinariate
orientalism
orientalist
orientation
originality
origination
ornithology
ornithopter
orthocenter
orthocentre
orthography
orthopedics
orthopedist
orthopraxia
orthopteran
orthopteron
orthostates
orthostichy
oscillation
oscillogram
ostensorium
ostentation
osteoclasis
osteologist
osteoplasty
osteotomist
ostracoderm
Ouagadougou
outbuilding
outdistrict
outdwelling
outfighting
outmerchant
outquarters
outwardness
ovariectomy
overacidity
overanxiety
overaptness
overbravado
overbravery
overcasting
overcharger
overcharity
overclothes
overcoating
overcoyness
overdraught
overflexion
overfluency
overfrailty
overfreedom
overgarment
overhonesty
overlaxness
overlowness
overloyalty
overmeasure
overmodesty
overobesity
overpayment
overpotency
overproness
overrealism
oversadness
oversatiety
oversilence
overtension
overthrower
overvariety
overvoltage
oviposition
ovovitellin
Oxfordshire
oxidization
oxyaldehyde
oxychloride
oxygenation
oxygenicity
oxyhydrogen
oxysulphide
oysterwoman
ozonosphere

List Of 12-Letter Nouns That Start With “o”

obedientiary
Oberammergau
obligingness
obliteration
oblivescence
obmutescence
obscurantism
observership
obsoleteness
obstetrician
oceanography
ochlophobist
octosyllable
odontography
offendedness
officeholder
oleandomycin
olericulture
oligophrenia
olla-podrida
omnidistance
omnipresence
oneirocritic
onomasiology
onomatopoeia
onychophagia
onychophoran
oophorectomy
ophthalmitis
opisthodomos
opposability
oppositeness
optimization
oracularness
orbicularity
orbiculation
orchestrater
orchestrator
orchidectomy
oreopithecus
organization
organography
organologist
orienteering
ornithomancy
ornithoscopy
orthocephaly
orthodontist
orthodoxness
orthogenesis
orthographer
orthopaedics
orthotropism
oscillograph
oscillometry
oscilloscope
ossification
osteichthyes
osteogenesis
osteomalacia
osteoporosis
otosclerosis
outrightness
outstretcher
ovariotomist
overanalysis
overcapacity
overcivility
overclemency
overcoolness
overcourtesy
overdearness
overdelicacy
overdilation
overdilution
overdrainage
overeasiness
overelegance
overemphasis
overexertion
overexposure
overfacility
overflatness
overfondness
overfoulness
overhugeness
overhumanity
overidealism
overinterest
overkeenness
overlewdness
overloudness
overlushness
overmeanness
overmeekness
overneatness
overoptimism
overoptimist
overrashness
overreaction
overreliance
overrichness
overrigidity
overrudeness
oversecurity
oversedation
overserenity
overseverity
overslowness
oversoftness
oversourness
overstocking
oversubtlety
oversureness
overtameness
overtartness
overtaxation
overtenacity
overthinness
overtimidity
overwariness
overweakness
overwideness
overwildness
oxyacetylene
objectiveness
obliviousness
obnoxiousness
observability
obstinateness
obstructivity
obtrusiveness
occasionalism
occasionality
occidentalism
occidentality
occlusiveness
oceanographer
octocentenary
odontoglossum
odoriferosity
oeil-de-boeuf
offensiveness
officiousness
oleomargarine
oligocythemia
one-sidedness
one-upmanship
onomatologist
opacification
operativeness
ophthalmology
opisthobranch
orchestration
orchidologist
organ-grinder
organicalness
organogenesis
organotherapy
ornamentality
ornamentation
ornithologist
orthogonality
orthohydrogen
osteomyelitis
ostracization
out-and-outer
outspokenness
overabundance
overacuteness
overaddiction
overagitation
overanimation
overappraisal
overassertion
overattention
overbraveness
overbrutality
overbulkiness
overcheapness
overcleanness
overcloseness
overcredulity
overcriticism
overcuriosity
overdecadence
overdiffusion
overdiligence
overdiversity
overdogmatism
overeagerness
overeducation
overemulation
overexpansion
overfaintness
overfertility
overfrailness
overfrankness
overfrequency
overfrugality
overgeniality
overgratitude
overgreatness
overgrossness
overhappiness
overharshness
overhastiness
overheadiness
overheaviness
overhostility
overimitation
overinflation
overinsolence
overintensity
overlactation
overlaudation
overlightness
overloftiness
overlooseness
overlustiness
overmagnitude
overmerriment
overmerriness
overnobleness
overnormality
overobedience
overobeseness
overpessimism
overplainness
overplenitude
overpotential
overprecision
overprolixity
overprovision
overpublicity
overquietness
overreadiness
overreduction
overretention
overrigidness
overroughness
oversecretion
overservility
oversolemnity
overstaleness
overstiffness
overstoutness
overstridence
overstridency
oversweetness
overtenseness
overthickness
overtightness
overtimidness
overtolerance
overtreatment
overvaluation
overvariation
overvehemence
oviparousness
ovoviviparism
ovoviviparity
oxidizability
oystercatcher

List Of 14-Letter Nouns That Start With “o”

objectlessness
obligatoriness
observableness
obstreperosity
obstructionism
obstructionist
occasionalness
octangularness
oleaginousness
olericulturist
omnivorousness
omphaloskepsis
openhandedness
operationalism
ophthalmometer
ophthalmometry
ophthalmoscope
ophthalmoscopy
oppressiveness
organisability
organizability
organographist
orthophosphate
orthoselection
otolaryngology
outlandishness
outrageousness
overabsorption
overaffliction
overallegiance
overassumption
overattachment
overbitterness
overbrightness
overbrilliance
overbrilliancy
overcapability
overcasualness
overcausticity
overcleverness
overcoloration
overcommonness
overcomplexity
overconfidence
overcorruption
overcostliness
overdaintiness
overdecoration
overdedication
overdependence
overdistention
overdistortion
overemployment
overenthusiasm
overestimation
overexcitement
overexuberance
overfemininity
overfierceness
overfloridness
overfluentness
overgenerosity
overgenialness
overgloominess
overgreasiness
overgreediness
overharassment
overheartiness
overhomeliness
overhonestness
overhumbleness
overindulgence
overinsistence
overinsistency
overinvestment
overirrigation
overjocularity
overjoyfulness
overjoyousness
overlavishness
overliberality
overliveliness
overlogicality
overluxuriance
overluxuriancy
overmatureness
overmellowness
overminuteness
overnarrowness
overnegligence
overpartiality
overpatriotism
overpersuasion
overpopularity
overpopulation
overpotentness
overprolixness
overprominence
overpromptness
overprotection
overpunishment
overrefinement
overreflection
overregulation
overremissness
oversaturation
overscepticism
oversettlement
oversevereness
oversilentness
oversimpleness
oversimplicity
oversmoothness
oversolemnness
overspeediness
oversteadiness
overstrongness
oversubscriber
overtenderness
oxidoreductase
oxyhaemoglobin

List Of 15-Letter Nouns That Start With “o”

obstructiveness
octogenarianism
odoriferousness
officialisation
officialization
olfactoreceptor
oligosaccharide
omnium-gatherum
oneirocriticism
open-mindedness
ophthalmologist
opinionatedness
opisthognathism
opprobriousness
ornithorhynchus
orthopsychiatry
otoneurasthenia
overabusiveness
overaffirmation
overaggravation
overanxiousness
overassuredness
overbashfulness
overbearingness
overbookishness
overcarefulness
overcomplacence
overcomplacency
overconsumption
overcontentment
overcontraction
overcopiousness
overcrowdedness
overcultivation
overcunningness
overdefiantness
overdemandiness
overdevelopment
overdevotedness
overdiffuseness
overdiverseness
overearnestness
overelegantness
overenviousness
overexpenditure
overexplanation
overfamiliarity
overfearfulness
overferventness
overfoolishness
overforwardness
overfrustration
overhelpfulness
overimportation
overinclination
overinstruction
overintenseness
overjealousness
overlearnedness
overlogicalness
overlubrication
overnervousness
overneutralizer
overnourishment
overoxidization
overpainfulness
overpartialness
overpensiveness
overpiteousness
overpreciseness
overpresumption
overproficiency
overprotraction
overprovocation
overreligiosity
overrestriction
overseriousness
overservileness
overskeptticism
overslavishness
oversparingness
overspeculation
overstimulation
oversufficiency
overtediousness
overthriftiness
overvaliantness
overventilation
overviolentness
overweeningness
overwillingness
overzealousness
oxytetracycline

List Of 16-Letter Nouns That Start With “o”

objectionability
obstreperousness
open-heartedness
ophthalmoscopist
opinionativeness
ostentatiousness
otolaryngologist
overacceleration
overaccentuation
overaccumulation
overappreciation
overapprehension
overboastfulness
overcaptiousness
overcarelessness
overcautiousness
overchildishness
overcivilization
overclinicalness
overcompensation
overcondensation
overconservatism
overconstantness
overcontribution
overcontriteness
overcovetousness
overcriticalness
overdeliberation
overdelicateness
overdenunciation
overderisiveness
overdesirousness
overdiligentness
overdiscreetness
overeffusiveness
overexcitability
overfactiousness
overfaithfulness
overfancifulness
overfruitfulness
overgraciousness
overgratefulness
overgrievousness
overillustration
overinterference
overliterariness
overlusciousness
overmercifulness
overmodification
overmournfulness
overnumerousness
overorganization
overpenalization
overpopulousness
overpositiveness
overpowerfulness
overpoweringness
overreservedness
overresoluteness
overrigorousness
oversanguineness
oversensibleness
overspaciousness
overstraightness
overstridentness
overstudiousness
oversubscription
overtechnicality
overtheorization
overtimorousness
overtrustfulness
overtruthfulness
overurbanization
overvaluableness
overvehementness
overvigorousness
overwhelmingness
objectionableness
occidentalization
old-fashionedness
orthogonalization
overambitiousness
overartificiality
overassertiveness
overattentiveness
overbounteousness
overbrutalization
overbumptiousness
overconcentration
overconsciousness
overconsideration
overcontentedness
overcourteousness
overcredulousness
overdefensiveness
overdeliciousness
overembellishment
overemotionalness
overexpansiveness
overexpectantness
overexuberantness
overfavorableness
overgesticulation
overgratification
overimitativeness
overindividualism
overindustrialism
overjudiciousness
overmagnification
overmasterfulness
overmelodiousness
overmodernization
overmystification
overnegligentness
overnormalization
overoffensiveness
overofficiousness
overornamentality
overplausibleness
overplentifulness
overpolemicalness
overponderousness
overpreoccupation
overprominentness
overpronunciation
overprovidentness
overqualification
overregimentation
overreligiousness
overrighteousness
overscepticalness
overskepticalness
oversorrowfulness
oversqueamishness
oversteadfastness
overtalkativeness
overtenaciousness
overventurousness
ovoviviparousness

List Of 18-Letter Nouns That Start With “o”

organotherapeutics
overabstemiousness
overaggressiveness
overcapitalisation
overcapitalization
overcensoriousness
overcentralization
overcharitableness
overcircumspection
overdecorativeness
overdeliberateness
overdepressiveness
overdiscouragement
overdogmaticalness
overemphaticalness
overexpressiveness
overfastidiousness
overgeneralization
overidolatrousness
overimpressibility
overinterestedness
overlasciviousness
overliberalization
overlicentiousness
overmultiplication
overneglectfulness
overneutralization
overobsequiousness
overparticularness
overpassionateness
overperemptoriness
overprosperousness
overreflectiveness
overrepresentation
overscrupulousness
oversentimentalism
oversentimentality
oversimplification
oversolidification
oversophistication
overspecialization
oversusceptibility
oversuspiciousness
overtheatricalness
overthoughtfulness

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