Definition of mg
mg: Abbreviation for milligram, a unit of measurement of mass in the metric system equal to a thousandth of a gram. A gram is equal to the mass of one milliliter, one thousandth of a liter, of water at 4 degrees C.
MG (in capital letters) is the abbreviation for the disease myasthenia gravis.
Last Editorial Review: 10/9/2012
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