pilv

Pilv is the Estonian word for a cloud. In meteorology, it denotes a visible aggregate of tiny water droplets and/or ice crystals suspended in the Earth's atmosphere. Clouds form when moist air rises or cools to its dew point, causing condensation on microscopic particles known as condensation nuclei. Their appearance and altitude reflect atmospheric conditions and the likelihood of precipitation.

Common cloud types are categorized by altitude (cirrus high, cirro-, alto-, stratus and cumulus at middle or low levels) as well as by form (cirrus, cumulus, stratus). Examples include cirrus (wispy high clouds), cumulus (puffy heaps), stratus (layered sheets), cumulonimbus (thunderclouds), and nimbostratus (rain clouds). Cloud classification is a basic tool in weather forecasting and climate studies; clouds influence daylight reflection (albedo) and surface temperatures and are indicators of atmospheric stability and moisture.

Clouds form through processes such as convection, frontal lifting, and orographic ascent, often involving condensation nuclei. Their evolution is studied with ground observations, radiosondes, and satellites, enabling forecasts of precipitation and weather patterns.

In Estonian, pilv is also used in the broader sense of cloud computing and cloud storage, as in pilveteenused or pilv-arvutus. The term reflects the metaphor of data stored in the cloud. The word is a cognate of Finnish pilvi and related Finnic languages.