In Euclid’s Geometry solids have boundaries which are called as surfaces.

 

Concept: According to Euclid's definition,

"A solid has shape, size, position, and can be moved from one place to another. Its boundaries are called surfaces. They separate one part of the space from another, and are said to have no thickness. The boundaries of the surfaces are curves or straight lines. These lines end in points."

This definition states that boundaries of solids are called surfaces.