The term 'tropical' refers to both the geographic origin of these systems, which form almost exclusively in tropical regions of the globe, and their formation in maritime tropical air masses. The term 'cyclone' refers to such storms' cyclonic nature, with anticlockwise rotation in the Northern Hemisphere and clockwise rotation in the Southern Hemisphere. Depending on its location and intensity, a tropical cyclone can be referred to by names such as 'hurricane', 'typhoon', 'tropical storm', 'cyclonic storm', 'tropical depression', or simply 'cyclone'.
Surrounding the eye of the hurricane is a ring of thunderstorms, called the eyewall. Rainbands surround the eye of the storm in concentric circles. In the eyewall and in the rainbands, warm, moist air rises, while in the eye and around the rainbands, air from higher in the atmosphere sinks back toward the surface. The rising air cools, and water vapor in the air condenses into rain. Sinking air warms and dries, creating a calm, cloud-free area in the eye.