(in the broad sense) a rapidly rotating storm system characterized by a low-pressure center, strong winds, and a circular/spiral arrangement of thunderstorms that produce heavy rain, ranging in increasing strength from tropical depressions and tropical storm to hurricanes.

(biochemistry) A hormone that regulates the activity of the endocrine glands

(geography) The parallel of latitude 23°30′north of the equator, marking the northern boundary of the tropics; the sun is directly overhead at the June solstice.

(geography) The parallel of latitude 23°30′south of the equator, marking the southern boundary of the tropics; the sun is directly overhead at the December solstice.

The time that it takes for the Sun to return to the same position along the ecliptic, as viewed from the Earth, especially: / A vernal equinox year, the time between two successive vernal equinoxes.

(meteorology) organized low-pressure system of thunderclouds with closed surface circulation and maximum sustained winds of less than 34 knots (63 km) per hour.

(medicine) any infectious disease which occurs only, or more often, in tropical or subtropical regions

Not tropical; not characteristic of or located in the tropics.

A cyclone within the tropics, typically having its thunderclouds organized in a spiral shape with wind speeds on the surface between about 30 and 75 miles (60 - 120 km) per hour.

(mathematics) A recent branch of geometry that can be described as a piecewise linear version of real algebraic geometry.