**1. . []**

Pertaining to structures in which the shapes of adjacent layers resemble or conform to one another. Folds of rock layers that have similar mechanical properties or competence tend to be harmonic, with little change in fold shape, symmetry or wavelength from one layer to the next.

**Antonyms:**
disharmonic

**See:**
competent,
concentric fold,
parallel fold,
similar fold,
structure

**2. . []**

A set of data values related by some function of frequencies and capable of being represented by sine and cosine functions.

**See:**
frequency

**3. . []**

A particular frequency at which a dataset has a resonance, or the frequency has special significance.

**See:**
Fourier analysis