C (English)
- Circle area
- Circle equation
- Circle of curvature
- Circle packing
- Circles of a triangle
- Circle theorem
- Circuit
- Circular cone
- Circular function
- Circular helix
- Circular motion
- Circumcenter
- Circumcentre
- Circumcircle
- Circumference
- Circummedial triangle
- Circumradius
- Circumscribe
- Circumscribed circle
- Circumsphere
Funded by: EU Socrates Minerva, HeyMath!, Cambridge University Press