Cross section (geometry)

Projection of a solid body onto a plane in 3D space, or an intersection of the two
Colored regions are cross-sections of the solid cone. Their boundaries (in black) are the named plane sections.

Cavalieri's principle states that solids with corresponding cross-sections of equal areas have equal volumes.

Cross-sections are often used in anatomy to illustrate the inner structure of an organ, as shown at the left.