Countable Nouns Starting with OP and Containing UM

Explore 8 verified English countable nouns starting with OP and containing UM, including Optimum, Opossum, Operculum, Oppidum, Opusculum, Opsonium and Ophidiarium. 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 OPE
1 words
operculum
Starts with OPH
2 words
ophidiarium
ophthalmophyllum
Starts with OPO
1 words
opossum
Starts with OPP
1 words
oppidum
Starts with OPS
1 words
opsonium
Starts with OPT
1 words
optimum
Starts with OPU
1 words
opusculum

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