Cloud

A cloud is a visible mass of condensed water droplets or ice crystals suspended in the atmosphere. Clouds form when air containing water vapor rises and cools, causing condensation on aerosols. They are a central component of the weather and climate system.

Clouds develop through vertical or horizontal air motions, including convection and orographic lifting. As rising air expands and cools, water vapor condenses into droplets; when many droplets combine, precipitation such as rain or snow may result. Cloud properties depend on temperature, humidity, and altitude.

Clouds are commonly classified by altitude and appearance. Low clouds include cumulus, stratocumulus, and stratus; mid-level clouds include altostratus and altocumulus; high clouds include cirrus, cirrostratus, and cirrocumulus. A separate category, cumulonimbus, denotes strong vertical development associated with thunderstorms.

In meteorology, cloud observations aid weather forecasting and climate monitoring. Cloud cover influences surface radiation and the energy balance, affecting atmospheric circulation, precipitation patterns, and ecological systems.

In computing, the term cloud refers to on-demand access to shared computing resources hosted remotely, enabling services such as infrastructure as a service (IaaS), platform as a service (PaaS), and software as a service (SaaS). Cloud computing offers scalability and flexibility but raises concerns about security, privacy, and dependence on network connectivity.