High Quality Content by WIKIPEDIA articles! The second moment of area, also known as "moment of inertia of plane area", "area moment of inertia", or "second area moment", is a property of a cross-section that can be used to predict the resistance of a beam to bending and deflection around an axis that lies in the cross-sectional plane. The stress in, and deflection of, a beam under load depends not only on the load but also on the geometry of the beam`s cross-section: larger values of second moment cause smaller values of stress and deflection. This is why beams with larger second moments of area, such as I-beams, are used in building construction in preference to other beams with the same cross-sectional area.