IPA: /ˈmɪl.reɪs/
KK: /ˈmɪlˌreɪs/
A water channel that directs water to a mill wheel, helping it to turn and generate power.
The old millrace was still in use, providing water to the historic mill.
Millrace → The word is formed from "mill" (from Old English *mylen*, meaning a place for grinding grain) and "race" (from Old English *ræce*, meaning a channel or course). A millrace refers to the channel that directs water to a mill for the purpose of grinding grain.
Think of a 'place for grinding grain' ('mill') and a 'channel' ('race') that brings water to it — that's how a millrace works.