Flatness

Flatness may refer to:
 * Flatness (art)
 * Flatness (cosmology)
 * Flatness (liquids)
 * Flatness (manufacturing), a geometrical tolerance required in certain manufacturing situations
 * Flatness (systems theory), a property of nonlinear dynamic systems
 * Spectral flatness
 * Flat intonation
 * Flat module in abstract algebra
 * Flat morphism in category theory