Moment-resisting frames are essential in the construction of sturdy buildings that can withstand lateral forces such as wind or earthquakes. These frames are commonly used in high-rise buildings, bridges, tunnels and other structures that require high strength and stability. Synonyms for the term "moment-resisting frame" include "rigid frame", "fixed frame", "sway-resistant frame" and "portal frame". These frames are designed to resist moments or forces that try to bend, twist or sway the structure. They are typically made of steel, reinforced concrete or other materials that can bear high loads and stress. The word "moment" refers to a force that tries to bend or twist a structure, while "resisting" means to withstand or oppose that force.