o, O O. oak oar oasis oat oath oatmeal obedient obese obey obi object objection objective obligate obligation oblige oblique angle oblong oboe obscure observation observatory observe obsolete obstacle obstruct obstruction obtain obtuse angle obvious occasion occasional occupant occupation occupy occur occurrence ocean ocean floor oceanography ocelot o’clock Oct. octagon octave October octopus odd oddity odds odor odorless of off offend offense offensive offer office officer official offset offshoot offshore offspring often ogre oh OH Ohio oil oil paint oil well oily ointment OKą OK˛ Okla. Oklahoma okra old olden Old English old-fashioned Old Testament Old World oleomargarine olive olive oil Olympic games omelet omen ominous omit omnivore on ON once oncoming one oneself one-sided one-way onion only onset Ont. Ontario onto onward ooze opal opaque open opener opening opera operate operation operator operetta opinion opossum opponent opportunity oppose opposite opposition oppress optical optimistic optional or -or OR oral orange orangeade orangutan orbit orchard orchestra orchid ordain ordeal order orderly ordinal number ordinarily ordinary ore Ore. or Oreg. Oregon organ organic organism organization organize Orient Oriental origin original originality originally originate oriole ornament ornate orphan orphanage orthodontist orthodox ostrich other otherwise otter ouch ought ounce our ours ourselves -ous oust out out- outboard motor outbreak outburst outcome outcry outdated outdid outdo outdone outdoor outdoors outer outer space outfield outfit outgoing outgrew outgrow outgrown outing outlaw outlet outline outlook outlying outnumber out-of-date outpost output outrage outrageous outran outrigger outright outrun outside outskirts outsmart outspoken outstanding outward outwards outwit oval ovary oven over over- overalls overboard overcame overcast overcoat overcome overdid overdo overdone overdose overdress overdue overeat overflow overflown overgrew overgrow overgrown overhand overhaul overhead overhear overheard overjoy overlap overload overlook overnight overpass overpower overran overrule overrun overseas overshoe oversight overtake overtaken overthrew overthrow overthrown overtime overtook overture overweight overwhelm overwork owe owl own owner ox oxcart oxen oxford oxide oxidize oxygen oyster oz. ozone