1. The season of the year between summer and winter, during which the weather becomes cooler and many plants become dormant, extending in the Northern Hemisphere from the autumnal equinox to the winter solstice and popularly considered to include the months of September, October, and November; fall. In the Southern Hemisphere autumn includes March, April, and May.
2. A period of maturity verging on decline.
1. Relating to or occurring in autumn: autumn foliage; autumn harvests.
2. Grown during the season of autumn: autumn crops.
[Middle English autumpne, from Old French autompne, from Latin autumnus.]
au·tumnal (ô-tŭmnəl) adj.
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2020 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Indo-European & Semitic Roots Appendices
Thousands of entries in the dictionary include etymologies that trace their origins back to reconstructed proto-languages. You can obtain more information about these forms in our online appendices:
The Indo-European appendix covers nearly half of the Indo-European roots that have left their mark on English words. A more complete treatment of Indo-European roots and the English words derived from them is available in our Dictionary of Indo-European Roots.