Amplitude of vibration

Vibration Vi*bra"tion, n. [L. vibratio: cf. F. vibration.] 1. The act of vibrating, or the state of being vibrated, or in vibratory motion; quick motion to and fro; oscillation, as of a pendulum or musical string. [1913 Webster]

As a harper lays his open palm Upon his harp, to deaden its vibrations. --Longfellow. [1913 Webster]

2. (Physics) A limited reciprocating motion of a particle of an elastic body or medium in alternately opposite directions from its position of equilibrium, when that equilibrium has been disturbed, as when a stretched cord or other body produces musical notes, or particles of air transmit sounds to the ear. The path of the particle may be in a straight line, in a circular arc, or in any curve whatever. [1913 Webster]

Note: Vibration and oscillation are both used, in mechanics, of the swinging, or rising and falling, motion of a suspended or balanced body; the latter term more appropriately, as signifying such motion produced by gravity, and of any degree of slowness, while the former applies especially to the quick, short motion to and fro which results from elasticity, or the action of molecular forces among the particles of a body when disturbed from their position of rest, as in a spring. [1913 Webster]

{Amplitude of vibration}, the maximum displacement of a vibrating particle or body from its position of rest.

{Phase of vibration}, any part of the path described by a particle or body in making a complete vibration, in distinction from other parts, as while moving from one extreme to the other, or on one side of the line of rest, in distinction from the opposite. Two particles are said to be in the same phase when they are moving in the same direction and with the same velocity, or in corresponding parts of their paths. [1913 Webster]