rotula /rotˈū-lə/

1. The knee-cap (anatomy)
2. A radial piece of Aristotle's lantern in sea-urchins (zoology)

• double-spacing
• double spare
• doublespeak
• double spread
• double standard
• double standards
• double star
• double stars
• double-stopping
• double-storey
• double-stout
• doublet
• double take
• double takes
• double-talk
• doublethink
• doublethinks
• double-threaded screw
• double-threaded screws
• double time
• doubleton
• double-tongue
• double-tongued
• double-tongues
• double-tonguing