amplitude (ˈæmplɪˌtjuːd)  
—n  
1.  greatness of extent; magnitude 
2.  abundance or copiousness 
3.  breadth or scope, as of the mind 
4.  astronomy the angular distance along the horizon measured from true east or west to the point of intersection of the vertical circle passing through a celestial body 
5.  maths Compare modulus See also Argand diagram Also called: argument (of a complex number) the angle that the vector representing the complex number makes with the positive real axis. If the point (x, y) has polar coordinates (r, θ), the amplitude of x + iy is θ, that is, arctan y/x 
6.  physics the maximum variation from the zero or mean value of a periodically varying quantity 
[C16: from Latin amplitūdō breadth, from amplus spacious] 
amplitude (ām'plĭtd') Pronunciation Key

amplitude
in physics, the maximum displacement or distance moved by a point on a vibrating body or wave measured from its equilibrium position. It is equal to onehalf the length of the vibration path. The amplitude of a pendulum is thus onehalf the distance that the bob traverses in moving from one side to the other. Waves are generated by vibrating sources, their amplitude being proportional to the amplitude of the source
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