noun

1. a modulating or being modulated; specif.,
   1. Music a shifting from one key to another
   2. Radio a variation in the amplitude, frequency, or phase of a wave in accordance with some signal
2. a variation in stress or pitch in speaking, as in distinguishing between the merely auxiliary and the lexical uses of a word (Ex.: “There is a post office on Main Street,” as contrasted with “There is the post office”)

Etymology: ME modulacioun < L modulatio