What is the gaseous region surrounding a planet called?

The gaseous region surrounding a planet is referred to as the atmosphere. This term encompasses all the layers of gases that are held in place by the planet's gravity, playing a crucial role in supporting life and regulating temperature. The atmosphere is composed of various gases, including nitrogen, oxygen, carbon dioxide, and trace amounts of other elements and compounds. It not only provides the air we breathe but also protects the planet from the harmful effects of solar radiation and cosmic rays, as well as helps to maintain moisture and climate conditions.

Other specific terms, such as stratosphere and exosphere, refer to particular layers within the Earth's atmosphere, with the stratosphere being situated above the troposphere and the exosphere being the outermost layer of the atmosphere. However, these terms do not encompass the entire gaseous region; rather, they represent specific sections of the overall atmospheric structure, making "atmosphere" the most accurate and comprehensive term for the gaseous envelope surrounding a planet.