The term aerosol describes a very fine mixture, or dispersion, of solid or liquid particles and a gas. In most cases, this gas is air.

The behavior of an aerosol always depends on the particles and the carrier gas. The suspended particles are called aerosol particles. An aerosol is a dynamic system and is subject to constant changes due to condensation of vapors on already existing particles, evaporation of liquid components of particles or deposition of particles on surrounding objects.