n (mathematics) The standard representation of such a space in 3-dimensional Euclidean space: a shape consisting of a ring with a circular cross-section: the shape of an inner tube or hollow doughnut.
n (topology|in combination|'n-torus'|'4-torus'|etc.) The product of the specified number of circles.
n (architecture) A molding which projects at the base of a column and above the plinth.
n (botany) The end of the peduncle or flowerstalk to which the floral parts (or in the Asteraceae, the florets of a flower head) are attached; see receptacle.