Related Clues:

• Hand holders?
• They're larger than radii
• Circle lines
• Cuts into a pie, often
• They help make joints
• Parts of arms
• Lines in a circle
• They go straight in a circle
• They parallel radii
• They're half the diameter
• Shadows on an equatorial sundial, say
• Halves of diameters
• r's, in math
• They start in the middle
• Semi-diameters