Abbreviation for microgram, a unit of mass equal to one millionth of a gram. Commonly used in medicine and chemistry for measuring very small quantities.
From the Greek letter mu (μ) representing 'micro-' (one millionth) and 'gram' from Greek 'gramma' meaning 'small weight.' The 'mcg' abbreviation is used to avoid confusion with 'mg' (milligram).
The abbreviation 'mcg' is preferred over 'μg' in medical settings because handwritten Greek mu can be misread as 'm', potentially leading to dangerous dosing errors. One microgram is so small that a grain of salt contains approximately 58,000 micrograms!
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