1. The ordinal number of forty-five in counting order
   - forty-fifth

See also: ordinal

• opéra bouffe
• or
• OR circuit
• or else
• OR gate
• or so
• ora
• orach
• orache
• oracle
• Oracle of Apollo
• oracle of Delphi
• oracular
• orad
• Oradexon
• oral
• oral cancer
• oral cavity
• oral communication
• oral contraception
• oral contraceptive
• oral contraceptive pill
• oral contract
• oral exam
• oral examination