A season is a division of the year, marked by changes in weather, ecology, and hours of daylight.
Seasons result from the yearly revolution of the Earth around the Sun and the tilt of the Earth's axis relative to the plane of revolution.
In temperate and polar regions, the seasons are marked by changes in the intensity of sunlight that reaches the Earth's surface, variations of which may cause animals to go into hibernation or to migrate, and plants to be dormant....
In temperate and subpolar regions generally four calendar based seasons are recognized: Spring, Summer, Autumn, and Winter....
In some tropical and subtropical regions it is more common to speak of the rainy (wet/monsoon) season versus the dry season...
In some parts of the world, special "seasons" are loosely defined based upon important events such as a hurricane season, tornado season or a wildfire season.
Autumn is one of the four temperate seasons. Autumn marks the transition from summer into winter, usually in March (Southern Hemisphere) or September (Northern Hemisphere) when the arrival of night becomes noticeably earlier.... Before the 16th century, harvest was the term usually used to refer to the season.... The alternative word fall is now mostly a North American English word for the season.... Autumn is nonetheless preferred in scientific and often in literary contexts. - Wikipedia