A unit of mass equal to one thousandth (10-3) of a milligram or one millionth (10-6) of a gram.(noun)
American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Use "microgram" in a sentence
"It takes 1000 grams to make a kilogram, so that means a microgram is a billionth of a kilogram."
"Each dose contains 50 micrograms (a microgram is one-millionth of a gram and a gram is the weight of one-fifth of a teaspoon of water)."
"A microgram is a millionth of a gram; a deciliter is one-tenth of a liter."