Countable Nouns Starting with O and Containing TO

Explore 138 verified English countable nouns starting with O and containing TO, including Operator, Octopus, Ontology, Observatory, Orator, Objector and Olfactory. Browse these count nouns with singular and plural forms below, or review singular and plural count rules in our noun grammar guide.

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Starts with OB10 words
observatory
objector
obbligato
obturator
obstructor
obliterator
obviator
obligator
observator
objurgator
Starts with OC24 words
octopus
octogenarian
oculomotor
octothorp
octocopter
octothorpe
octoroon
octopod
octosyllabic
octopoid
octoploid
occipitofrontalis
octonary
octosyllable
occipitoposterior
octodecimo
octofoil
octopodan
octodecillion
octostyle
octogenary
octocentenary
octonarius
octopusher
Starts with OD15 words
odontoid
odontoblast
odontocete
odontoma
odontologist
odontolite
odontophore
odontograph
odontophobia
odontornithes
odonatologist
odontoglossum
odontography
odontophoran
odontopteryx
Starts with OF
2 words
offertory
officiator
Starts with OI
1 words
oilstone
Starts with OL7 words
olfactory
olinguito
olfactologist
olfactometer
olitory
olfactophobia
oleorefractometer
Starts with OM
2 words
ommatophore
omentosplenopexy
Starts with ON8 words
ontology
onomatopoeia
ontogeny
ontologist
onomatopoiesis
onychocryptosis
onomatologist
oncotomy
Starts with OO4 words
oophorectomy
oophorosalpingectomy
oophorhysterectomy
oophorocystectomy
Starts with OP14 words
operator
optometrist
operatorship
opinionator
optocoupler
opisthotonos
optometer
optophone
ophthalmostatometer
optologist
ophthalmotonometer
ophthalmomyotomy
ophthalmophlebotomy
optomeninx
Starts with OR12 words
orator
oratory
originator
orchestrator
oratorio
orchiectomy
ortolan
orientator
oratorian
orchidectomy
orbitosphenoid
orthotone
Starts with OS7 words
oscillator
ostomy
osteotomy
ostinato
ostomate
osculatory
osteotome
Starts with OT13 words
ottoman
otto
otoscope
oto
otolith
otorhinolaryngologist
otoplasty
otologist
otoscopy
otocinclus
otosclerotic
otocyst
otosalpinx
Starts with OU
1 words
outoffice
Starts with OV11 words
overtone
overstock
overstory
ovariectomy
ovipositor
oviraptor
ovariohysterectomy
ovariotomy
ovariotomist
ovator
ovariosalpingectomy
Starts with OX5 words
oxygenator
oxtongue
oxytocic
oxytone
oxytonic

•Browse Countable Nouns by Letter (A to Z)

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