A column is a vertical monolithic structure which is either carved out of rock or designed to give that appearance, and which has a clearly defined division into base, shaft, and capital.

The base, shaft, and capital are visibly distinct parts of the vertical form. The structure can be solid rock or another construction giving that appearance.

An obelisk instead has a tapering square shaft ending in a pyramidal cap. A simple menhir lacks the developed base-and-capital articulation described here.