A structural member that carries its load in compression along its length. Most frequently, as in a building, the column is in a vertical position transmitting gravity loads from its top down to its base. Columns are present in other structures as well, such as in bridges, towers, cranes, airplanes, machinery, and furniture. Other terms used by both engineers and lay persons to identify a column are pillar, post, and strut. Columns of timber, stone, and masonry have been constructed since the dawn of civilization; modern materials also include steel, aluminum, concrete, plastic, and composite material.