0 3000 Common English Words – O o'clockobjectobjectiveobservationobserveobtainobviousobviouslyoccasionoccasionallyoccupiedoccuroceanoctoberoddoddlyofoffoffenceoffendoffensiveofferofficeofficerofficialofficiallyoftenoilok (okay)oldold-fashionedonceoniononlyontoopenopeningopenlyoperateopinionopponentopportunityopposeoppositeoppositionoptionorangeorderordinaryorganizationorganizeorganizedoriginoriginaloriginallyotherotherwiseouroursourselvesoutoutdooroutdoorsouteroutlineoutsideoutstandingovenoveroverallovercomeoweownowner