The basic understanding of loads, stresses, and deformations obtained in the preceding chapters is related here to columns. A column is straight and long (relative to its cross section) and is subjected to compressive, axial loads. The reason for a special consideration of columns is that failures due to yielding, determined from Eq. (4.22), and due to deformation, determined from Eq. (4.23), are not correct in predicting failures of long columns. Because of their slender shape, columns tend to deform laterally upon loading; and if the deflection becomes larger than their respective critical values, they fail catastrophically. This situation is known as buckling, which can be defined as a sudden large deformation of a structure due to a slight increase of the applied load, under which the structure had exhibited little, if any, deformation before this increase.