Countable Nouns Starting with O and Containing IS

This list gathers 166 English countable nouns starting with O and containing IS, such as Organism, Omission, Oasis, Optimist, Opportunist, Osmosis and Oncologist. Use the sorting controls below to organize entries by length, or consult our noun grammar guide to review singular and plural count rules.

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Starts with OA
2 words
oasis
oarfish
Starts with OB11 words
obelisk
obeisance
obstructionist
objectivist
oboist
obscurantist
obituarist
obsoletism
obeliskoid
obeliscoid
obsessionist
Starts with OC11 words
occultist
oculist
occidentalism
occasionalism
occidentalist
ocularist
oceanologist
occasionalist
occipitofrontalis
ockerism
octakishexahedron
Starts with OD6 words
odalisque
odist
odontologist
odontist
odonatologist
odonatist
Starts with OE3 words
oenologist
oenophilist
oecist
Starts with OG
2 words
ogrefish
oghamist
Starts with OI
2 words
oilfish
oikist
Starts with OL5 words
ologist
oligopolist
olfactologist
oligist
olecranarthritis
Starts with OM4 words
omission
omniscient
omnisexual
omnishambles
Starts with ON11 words
oncologist
ontologist
onanist
onomatopoiesis
onychocryptosis
onomatologist
onychitis
oncogeneticist
onychophagist
oniscoid
oneiroscopist
Starts with OO
1 words
oologist
Starts with OP24 words
optimist
opportunist
optometrist
ophthalmologist
oppositionist
operationalist
opinionist
opisthosoma
opisthotonos
ophthalmist
operationist
operettist
ophiologist
opisthobranch
opisthograph
opisometer
opticist
opisthography
ophiophilist
opisthodomos
ophthalmoscopist
ophthalmomycosis
opisthopulmonate
opisthobranchiate
Starts with OR24 words
organism
orthodontist
organist
orientalism
ornithologist
originalist
orientalist
orthopedist
orisha
orison
organogenesis
orris
orbicularis
orthotist
orchardist
orchis
orrisroot
orthosis
orogenesis
oralist
organicist
orthoptist
ornithischian
orchidist
Starts with OS10 words
osmosis
ostracism
osteonecrosis
osteomyelitis
osteoarthrosis
osteopetrosis
osteologist
osteopathist
osteoclasis
ostreiculturist
Starts with OT
2 words
otorhinolaryngologist
otologist
Starts with OU
2 words
ouistiti
ourisia
Starts with OV17 words
overemphasis
overdiagnosis
overanalysis
overissue
overoptimist
ovotestis
overissuance
overregistration
ovisac
overpoise
ovist
overembellishment
ovariotomist
overdiscount
overflourish
overdiscouragement
overdiscrimination
Starts with OX
2 words
oxalis
oxisol
Starts with OZ
1 words
ozonolysis

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