Define the following terms in detail: Beam , bending stress, and bending moment.

Beam: A beam is a structural element that primarily resists loads applied laterally to the beam's axis. Its mode of deflection is primarily by bending. The loads applied to the beam result in reaction forces at the beam's support points. The total effect of all the forces acting on the beam is to produce shear forces and bending moments within the beam, that in turn induce internal stresses, strains and deflections of the beam. Beams are characterized by their profile (shape of cross-section), their length, and their material.

Bending Stress: Bending stress is a more specific term for the stress developed in a beam's material due to an external moment or a changing moment along the length of the beam. It is the combination of compressive stress in one side of the beam's neutral axis, and tensile stress on the other side, caused by the beam's bending. The maximum bending stress occurs at the furthest points from the neutral axis, which are the top and bottom surfaces of the beam.

Bending Moment: Bending moment at a section of a beam is the sum of the moments about that section of all external forces acting to one side of that section. The bending moment at any location along the beam can then be used to calculate the bending stress over the beam's cross section at that location. The bending moment at a cut section is defined as the algebraic sum of the moments about the section of all forces acting on one side of the section.