Type of pure waveform having an equal distance from its peak to the zero or center line and from its trough to the center line and in which the positive hump and negative hump of the wave are exactly equal in length, shape and height but flipped in a mirror image about the center line. Sine waves repeat exactly their shape over their wavelength, which consists of one positive and one negative hump or lobe. Each wavelength repeats exactly the same pattern into infinity. Sine waves are the basis for other waveforms. They are also the basis for test tones and a measure of pure performance.