numero uno/ˌnoohməroh ʹoohnoh/ noun

• operatic
• operatics
• operating system
• operating table
• operating theatre
• operation
• operational
• operationalism
• operational research
• operations research
• operations room
• operative
• operator
• operculum
• operetta
• operon
• ophicleide
• ophidian
• ophite
• ophthalm-
• ophthalmia
• ophthalmic
• ophthalmic optician
• ophthalmo-
• ophthalmologist