quartet, quartette or quartett /kwör-tetˈ/

1. A set of four
2. A composition for four voices or instruments
3. A set of performers or instruments for such compositions

• opus Dei
• opuses
• opus latericium
• opus musivum
• opus operantis
• opus operatum
• opus reticulatum
• OPW
• opéra bouffe
• opéra comique
• -or
• or
• OR
• Or.
• ora
• orach
• orache
• oraches
• oracies
• oracle
• oracled
• oracles
• oracling
• oracular
• oracularities