in atmospheric chemistry
A small liquid particle. The size of droplets encountered in the atmosphere extends over a wide range; e.g. liquid aerosol solutions which make up the fine particle fraction of continental tropospheric aerosol are usually 2 µm in diameter. Cloud water droplets usually have diameters in the range of 5-70 µm, while rain droplets commonly have diameters ranging from 0.1-3 mm.
PAC, 1990, 62, 2167. 'Glossary of atmospheric chemistry terms (Recommendations 1990)' on page 2185 (https://doi.org/10.1351/pac199062112167)