What is a thing (only in phrase below). Rule of Coss, an old name for Algebra. Etym: [It. regola di cosa rule of thing, the unknown quantity being called the cosa, or the thing.] called?

coss — A thing (only in phrase below). Rule of Coss, an old name for Algebra. Etym: [It. regola di cosa rule of thing, the unknown quantity being called the cosa, or the thing.]. (Webster's 1913.)

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