The stratosphere, a layer of Earth's atmosphere located above the troposphere, is characterized by its stable temperature and the presence of the ozone layer. Synonyms for this term include the upper atmosphere, the ozone layer, and the mid-atmosphere. The upper atmosphere encompasses the stratosphere and the higher regions of the atmosphere, while the ozone layer refers specifically to the area where ozone concentrations are highest. The mid-atmosphere is a less commonly used term that refers to the region between the troposphere and the mesosphere. These various phrases are all useful in describing the layer of Earth's atmosphere that plays a critical role in protecting life on our planet.