cirrus

Cirrus refers primarily to a genus of high-altitude clouds in Earth's atmosphere. Cirrus clouds are formed in the upper troposphere, usually above 6,000 meters (about 20,000 feet), and are composed mostly of ice crystals. They appear as thin, wispy, hairlike strands that are white and translucent. Because of their high altitude, they rarely produce precipitation that reaches the ground, but they can indicate moisture aloft and often precede changes in the weather, such as the approach of a warm front.

In cloud classification, cirrus is one of the high-cloud genera and can occur in several species and forms. Commonly cited varieties include cirrus fibratus (fibrous, filamentous), cirrus uncinus (hook-shaped), cirrus spissatus (dense or packed), and cirrus floccus (tufted). These clouds may occur alone or in combination with other high-cloud types, such as cirrostratus or cirrocumulus. Cirrus can also produce optical phenomena such as halos around the sun or moon when ice crystals refract light.

Beyond meteorology, the term Cirrus is used in several brand and company names. Cirrus Aircraft is an American aircraft manufacturer known for models such as the SR-series and the SF50 Vision Jet, noted for integrating a whole-airframe parachute system. Cirrus Logic is a semiconductor company that designs and markets audio and voice-processing integrated circuits used in consumer electronics. The name is commonly associated with aviation and atmospheric science, in addition to its cloud-related meaning.