on-s - outg
- open-air address
- open-and-shut case
- open-door policy
- open-ended bureau
- opening
- opening address
- opening ceremony
- opening day of the trial
- opening of a congress
- opening of the debate
- opening remarks
- opening session
- opening shots in the conflict
- opening sitting
- opening sitting of a congress
- opening speech
- opening statement
- openly pursued policy
- openness
- openness at home
- opera house
- operate
- operated establishment
- operating
- operating costs
- operating data
- operating establishment
- operating expenditures
- operating expenses
- operating period
- operating personnel
- operating plan
- operating procedure
- operating ratio
- operating records
- operating reserve
- operating revenue
- operating rules
- operating staff
- operating time
