Slenderness ratio is the ratio of the effective length of a column (Le) and the least radius of gyration (r) about the axis under consideration. It is given by the symbol “λ” (lambda).
Effective slenderness ratio of the section about the minor axis of cross-section = Le/ry.
Effective slenderness ratio of the section about the major axis of cross section = Le/rx.
As slenderness ratio increases, permissible stress or critical stress reduces. Consequently, load carrying capacity also reduces.