What is a buttress in architectural terms?

In architectural terms, a buttress refers to an architectural structure that is specifically designed to support and strengthen a wall. It serves a crucial role in stabilizing walls, especially those that bear significant weight or lateral forces, such as vaulted ceilings or large structures. The function of a buttress is to transfer the weight from the wall to the ground, which prevents the wall from bowing or collapsing under pressure. This structural element is particularly prominent in Gothic architecture, where flying buttresses are used to allow for higher ceilings and larger windows.

The other options don't accurately define a buttress: an ornamental design on a wall does not provide structural support, while a type of building material describes the substance from which structures are made rather than a specific support structure. A roof support, on the other hand, refers more to elements like beams or trusses designed to hold up the roof, which while related to structural support, does not encompass the unique purpose of a buttress.