Countable Nouns Starting with O and Containing OS

This list gathers 183 English countable nouns starting with O and containing OS, such as Opposition, Overdose, Outpost, Ostrich, Osmosis, Oscillation and Opossum. 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 OC5 words
octosyllabic
octosyllable
occipitoposterior
octostyle
occipitosphenoid
Starts with OD
1 words
odontoglossum
Starts with OL
2 words
oligosaccharide
oloroso
Starts with OM
2 words
omphalos
omentosplenopexy
Starts with ON5 words
oncost
onychocryptosis
onos
oncostman
oneiroscopist
Starts with OO4 words
oosphere
oospore
oophorosalpingectomy
oosperm
Starts with OP18 words
opposite
opposition
opossum
opposer
ophthalmoscope
oppositionist
ophthalmoscopy
opisthosoma
opisthotonos
operosity
opisthodomos
ophthalmoscopist
ophthalmomycosis
ophthalmostatometer
ophthalmodiagnosis
ophthalmomyositis
opeidoscope
ophthalmoleucoscope
Starts with OR14 words
organophosphate
organophosphorus
orthophosphate
orthosis
orthros
ornithomimosaur
orthosilicate
orthoscope
orthostat
organosol
orthostichy
orbitosphenoid
ornithosaur
orthrosanthus
Starts with OS24 words
oscars
ostrich
osmosis
oscillation
oscillator
osprey
ostracism
os
ostentation
ostomy
oscilloscope
osteopathy
osteopath
ossification
ostler
osmolarity
osteosarcoma
osteoid
osteria
ostia
ossuary
osteonecrosis
osteocyte
osteomyelitis
Starts with OT5 words
otoscope
otoscopy
otosclerotic
otiosity
otosalpinx
Starts with OU4 words
outpost
ouroboros
outcross
outcrossing
Starts with OV10 words
overdose
overexposure
overdiagnosis
oviposition
overdosage
overgenerosity
ovipositor
ovibos
overscrupulosity
ovariosalpingectomy
Starts with OZ
1 words
ozonosphere

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