What does milligram mean?
A milligram is a metric unit of mass equal to one-thousandth of a gram. It is used when the quantity being described is too small for grams to be convenient or sufficiently precise. Milligrams are common in medicine and pharmacology, especially on drug labels and in dosage instructions, as well as in nutrition, chemistry, biology, and commerce. The word is also frequently abbreviated as “mg,” allowing it to appear naturally in tables, scientific articles, packaging, and prescriptions. Although a milligram is a very small amount, it is still larger than a microgram, one-millionth of a gram. In everyday conversation, people may use the word to suggest a tiny quantity, but its primary role is precise measurement. It belongs to the metric system and is written in the same form in British and American English.
nounA metric unit of mass equal to one-thousandth of a gram. It is commonly used in medicine, science, nutrition, and trade to describe very small quantities.
- A metric unit of mass equal to one-thousandth of a gram, used for measuring very small quantities.
"The dose contains no more than 5 milligrams of the active ingredient."
"The laboratory recorded a change of only 2 milligrams in the sample."
"Nutrition labels list the recommended daily allowance in milligrams."
The standard plural adds “-s” and is used with quantities such as “a few milligrams” or “10 milligrams.”
"The study measured the concentration in milligrams per litre."
The prefix milli means one-thousandth, so a milligram is the tiny metric cousin of a gram.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does milligram come from?
Milligram was formed by combining the metric prefix milli, meaning one-thousandth, with gram. Gram itself comes through French and Latin from Greek gramma, a word associated with writing and a small unit of weight. The metric prefix and the gram formed a system in which units such as the milligram, centigram, and kilogram express related fractions or multiples of the same base unit.
Related word forms
How milligram is actually used
Milligram is a precise scientific and medical unit. The abbreviated form “mg” is widely used in dosage instructions, labels, and scientific writing; it should not be confused with the unrelated unit pound.
Easily confused with milligram
A milligram is one-thousandth of a gram, while a microgram is one-millionth of a gram.