Countable Nouns Starting with O and Containing UM

This list gathers 44 English countable nouns starting with O and containing UM, such as Optimum, Opossum, Ovum, Omnium, Omentum, Organum and Ouma. 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 OB
1 words
obumbration
Starts with OC
1 words
oceanarium
Starts with OD
2 words
odeum
odontoglossum
Starts with OI
1 words
oidium
Starts with OM5 words
omnium
omentum
omasum
ommatidium
ommateum
Starts with ON3 words
onium
oncidium
onychium
Starts with OO
1 words
oogonium
Starts with OP8 words
optimum
opossum
operculum
oppidum
opusculum
opsonium
ophidiarium
ophthalmophyllum
Starts with OR7 words
organum
origanum
ornithogalum
orarium
organistrum
orontium
ordalium
Starts with OS8 words
ostium
osculum
osmiridium
ostensorium
osteospermum
ossarium
osmeterium
osteoglossum
Starts with OU
1 words
ouma
Starts with OV4 words
ovum
overtrump
ovalbumin
overaccumulation
Starts with OX
2 words
oxonium
oxypetalum

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