That which alternates with something else; vicissitude.

(US) A substitute; an alternative; one designated to take the place of another, if necessary, in performing some duty.

(mathematics) A proportion derived from another proportion by interchanging the means.

(US) A replacement of equal or greater value or function.

(transitive) To perform by turns, or in succession; to cause to succeed by turns; to interchange regularly.

(intransitive) To happen, succeed, or act by turns; to follow reciprocally in place or time; followed by with.

(intransitive) To vary by turns.

(transitive, geometry) To perform an alternation (removal of alternate vertices) on (a polytope or tessellation); to remove vertices (from a face or edge) as part of an alternation.

Happening by turns, one following the other in succession of time or place, and can also refer to alternating colors in heraldry.

(mathematics) Designating the members in a series, which regularly intervene between the members of another series, as the odd or even numbers of the numerals; every other; every second.

(US) Other; alternative.

(botany, of leaves) Distributed singly at different heights of the stem, and at equal intervals as respects angular divergence