conundrum /kə-nunˈdrəm/

1. A riddle, esp one whose answer is a play on words
2. Any puzzling question

• concentrations
• concentrative
• concentrativeness
• concentrator
• concentrators
• concentre
• concentred
• concentres
• concentric
• concentrical
• concentrically
• concentricities
• concentricity
• concentring
• concents
• concentus
• concept
• conceptacle
• conceptacles
• concept album
• concept albums
• concept car
• concept cars
• concepti
• conception