A low hill at the base of a mountain or mountain range.
From 'foot' (base or lowest part) + 'hill' (elevated landform), an American English compound from 19th-century geography, describing mountains that have literal 'feet' of smaller hills.
Foothills are where mountains and plains negotiate their relationship—these transition zones are where civilizations naturally clustered, finding fresh water, fertile land, and protected shelter all at once.
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