An Etymological Dictionary of Astronomy and Astrophysics
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In communications, the process of recovering the original information from a modulated signal wave. → modulation.

→ de- + → modulation

General: The modification of some property of a phenomenon by another distinct phenomenon.
Physics: Variation of some characteristic (amplitude, phase, or frequency) of a radio wave, called the carrier wave, in accordance with instantaneous values of another wave, called the modulating wave. → amplitude modulation; → frequency modulation.
Optics: A synonym for contrast, particularly when applied to a series of parallel lines and spaces imaged by a lens.

Verbal noun of → modulate.

A measure of the ability of an optical system to reproduce (transfer) various levels of detail from the object to the image, as shown by the degree of contrast (modulation) in the image. → optical transfer function.

→ modulation; → transfer; → function.

Modulation in which the phase angle of a sine-wave carrier is caused to depart from the carrier angle by an amount proportional to the instantaneous magnitude of the modulating wave.

→ phase; → modulation.

A very small variation in the surface brightness of a single star due to its rotation. Several types of stars are known to have photospheric spots. Brightness variation occurs as rotation carries star spots or other localized activity across the line of sight.

→ rotational; → modulation.