A Jewish scholar or expert in halacha (Jewish law) who studies and interprets religious legal traditions.
From halacha (Jewish law) plus the suffix -ist (one who practices or specializes in). The formation follows English patterns for creating specialist nouns.
A halachist is to Jewish law what a constitutional scholar is to American law—they spend careers finding solutions to questions no one expected, like whether you can use a computer on the Sabbath.
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