counterpart /kownˈtər-pärt/

1. The part that answers to, fits into or completes another part, having the qualities which the other lacks
2. A corresponding or equivalent person or thing
3. A duplicate, a close or exact copy

• radio waves
• radish
• radishes
• radium
• radium A
• radium B
• radium bomb
• radium bombs
• radium emanation
• radiums
• radius
• radiuses
• radius of curvature
• radius vector
• radius vectors
• radix
• radome
• radomes
• radon
• radons
• rads
• radula
• radulae
• radular
• radulate