What is a pendentive used for in architecture?

A pendentive is a crucial architectural element designed to facilitate the transition of a square space to a dome. Specifically, it functions as a curved triangular section that aids in distributing the weight of the dome above by providing a stable, rounded base that connects the dome to the corners of the square room. This technique is particularly significant in the design of churches and other significant structures where a dome is desired, as it helps to manage the structural loads effectively.

In contrast to the other options, a pendentive does not support a column, decorate walls, or form the foundation. Its unique shape and structural purpose distinguish it as a specialized solution for integrating domes into square or rectangular spaces, thus enhancing both the aesthetic and functional aspects of architectural design.