https://xkcd.com/2825
Alt text:
Of course in reality this is just a US/UK thing; in British English, 'fall' is the brief period in between and 'autumn' is the main season.
https://explainxkcd.com/2825
The joke here is that, because Americans do not use the term "autumn" in normal communication, someone might be led to believe that it had a special unusual scientific meaning.
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https://explainxkcd.com/2825