PERITROCHIUM
, in Mechanics, is a wheel or circle, concentric with the base of a cylinder, and moveable together with it, about an axis. The axis, with the wheel, and levers sixed in it to move it, make that mechanical power, called Axis in Peritrochio, which see.
PERMUTATIONS of Quantities, in Algebra, the Alternations, Changes, or different COMBINATIONS of any number of things. See those terms.