1. Dentistry A hard yellowish deposit on the teeth, consisting of organic secretions and food particles deposited in various salts, such as calcium carbonate. Also called calculus.
2. A reddish acid compound, chiefly potassium bitartrate, found in the juice of grapes and deposited on the sides of casks during winemaking.
[Middle English tartre, tartar in wine casks, potassium bitartrate, from Old French, from Medieval Latin tartarum, perhaps alteration (perhaps influenced by Latin Tartarus, Tartarus, since tartar collects in the bottom of wine casks) of Arabic darādī, plural of durdī, lees, dregs, from Persian durdī, dregs, from durd, from Old Iranian *dti-, dirtiness, excrement (compare Sogdian δrt-, dung, manure); akin to Old Norse drit, dirt, and Lithuanian dergti, to dirty, defile.]
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Indo-European & Semitic Roots Appendices
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