A milligram (mg) is a unit of mass in the metric system and the International System of Units (SI). It is equal to one one-thousandth of a gram, which means that 1 milligram is equivalent to 0.001 grams. The milligram is a small unit of mass commonly used for measuring very small quantities of substances, especially in scientific, medical, and pharmaceutical contexts.
For example, when you see the dosage of a medication listed on a prescription or on over-the-counter drugs, it is often measured in milligrams. Additionally, in laboratory settings, chemicals and substances are frequently measured in milligrams due to its precision in measuring small quantities.
A "slug," in the context of mass, is a unit of measurement primarily used in the United States customary and British imperial systems. It is not a widely used unit and is considered somewhat archaic. The slug is used to measure mass and is defined as the mass that accelerates at a rate of one foot per second squared (1 ft/s²) when a force of one pound-force (1 lbf) is applied to it. In other words, a slug is the mass that results in an acceleration of 1 ft/s² when a force of 1 lbf is applied to it.