What is a beam, of any material that supports other beams called?

A beam that supports other beams is termed a girder. Girders are primary structural elements typically used in bridge, building, and other types of construction. They provide essential weight support and distribute loads to columns or walls. The notable characteristic of a girder is its ability to bear the considerable loads from beams, which in turn support floors or roofs and transfer those loads deeper into the structural framework.

In contrast, a lintel is a beam that spans an opening, such as a doorway or window, and is primarily used for making these openings structurally sound rather than supporting other beams. A grillage refers to a framework made of beams in a mutually supportive arrangement, often used in foundations but not specifically to describe a primary support beam. A cantilever beam is a specific type of beam fixed at one end and free at the other, which does not fit the description of a support beam for other beams.

Therefore, the term girder correctly identifies the larger beam that serves the necessary function of supporting additional beams within the structural system.