haze, suspension in the atmosphere of dry particles of dust, salt, aerosols, or photochemical smog that are so small (with diameters of about 0.1 micron [0.00001 cm]) that they cannot be felt or seen individually with the naked eye, but the aggregate reduces horizontal visibility and gives the atmosphere an opalescent appearance. Haze appears as a bluish or yellowish veil depending on whether the background is dark or light, respectively. With respect to these colours, haze can be discriminated from mist, which gives a grayish cast to the sky.