This subsection lists the definitions from Book 11 of "Euclid’s Elements". Euclid’s definitions avoid figures. At BookOfProofs, figures are given for the most definitions.

- Definition: Def. 11.01: Solid Figures, Three-Dimensional Polyhedra
- Definition: Def. 11.02: Surface of a Solid Figure
- Definition: Def. 11.03: Straight Line at Right Angles To a Plane
- Definition: Def. 11.04: Plane at Right Angles to a Plane
- Definition: Def. 11.05: Inclination of a Straight Line to a Plane
- Definition: Def. 11.06: Inclination of a Plane to a Plane
- Definition: Def. 11.07: Similarly Inclined Planes
- Definition: Def. 11.08: Parallel Planes
- Definition: Def. 11.09: Similar Solid Figures
- Definition: Def. 11.10: Equal Solid Figures
- Definition: Def. 11.11: Solid Angle
- Definition: Def. 11.12: Pyramid, Tetrahedron
- Definition: Def. 11.13: Prism, Parallelepiped
- Definition: Def. 11.14: Sphere
- Definition: Def. 11.15: Axis of a Sphere
- Definition: Def. 11.16: Center of a Sphere
- Definition: Def. 11.17: Diameter of a Sphere
- Definition: Def. 11.18: Cone
- Definition: Def. 11.19: Axis of a Cone
- Definition: Def. 11.20: Base of a Cone
- Definition: Def. 11.21: Cylinder
- Definition: Def. 11.22: Axis of a Cylinder
- Definition: Def. 11.23: Bases of a Cylinder
- Definition: Def. 11.24: Similar Cones, Similar Cylinders
- Definition: Def. 11.25: Cube
- Definition: Def. 11.26: Octahedron
- Definition: Def. 11.27: Icosahedron
- Definition: Def. 11.28: Dodecahedron