Known as fall in North America, autumn astronomically begins on the autumnal equinox (when the tilt of the Earth's axis is oriented neither from nor to the Sun causing the Sun to be located vertically above a point on the equator) and ends on the winter solstice (when the tilt of the Earth's axis is most oriented away from the Sun). The autumnal equinox occurs between September 22 or 23 in the Northern Hemisphere and on March 20 in the Southern Hemisphere. The winter solstice ending autumn occurs on December 21 or 22 in the Northern Hemisphere and June 21 in the Southern Hemisphere.

Meteorological autumn is the season when summer transitions into winter. In the Northern Hemisphere, meteorological autumn covers the entire months of September, October and November. In the Southern Hemisphere, meteorological autumn covers the entire months of March, April and May.

Before the 16th century, autumn was known as the harvest season. However, as the population migrated from the farms to the cities the term fell out of favor.

Besides known as the season for harvesting crops, autumn is also associated with brightly colored foliage. The two regions of the world most famous for this natural phenomenon are North America (Canada and the United States) and Eastern Asia (China, Korea, and Japan). Though not as dramatic, the autumn "changing of the leaves" can also be seen in parts of Europe, Argentina, Australia, Chile and New Zealand. In ancient China, autumn was known as White Tiger.