The season when the leaves fall from the trees WordNet 3.0 & Open English WordNet

Autumn, also known as fall in North American English, is one of the four temperate seasons on Earth. Wikipedia

One of the four temperate seasons. Wikipedia Disambiguation

One of the Earth's four temperate seasons, occurring between summer and winter Wikidata

The season after summer and before winter, traditionally from September 21 to December 20 in the northern hemisphere and from March 21 to June 20 in the southern hemisphere. OmegaWiki

Traditionally the third of the four seasons, when deciduous trees lose their leaves; typically regarded as being from September 24 to December 22 in parts of the Northern Hemisphere, and the months of March, April and May in the Southern Hemisphere. Wiktionary