harmonic analysis

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun The study of functions given by a Fourier series or analogous representations, such as periodic functions and functions on topological groups.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun analysis A study of the representation of functions or signals as the superposition of basic waves, involving the notions of harmonic functions, trigonometric series, Fourier series, Fourier transforms, almost periodic functions, and others.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun analysis of a periodic function into a sum of simple sinusoidal components