Glossary
metric prefix
A metric prefix names a power of ten applied to a base unit — kilo is 1,000, centi is one hundredth, milli is one thousandth — so converting between them moves the decimal point.
A metric prefix states which power of ten a base unit is being multiplied by. The prefixes this course drills are kilo (×1,000), centi (×1/100), milli (×1/1,000) and micro (×1/1,000,000) — so a kilogram is a thousand grams, a milliliter is a thousandth of a liter and a microgram is a millionth of a gram. Because every step is a power of ten, converting between metric units is a decimal-point move rather than a proportion: count the powers of ten between the two units and shift the point that many places, right when the unit is getting smaller and left when it is getting larger. Two errors recur. The point moves one place per power of ten, not one place per prefix: kilo to centi is five places, because 1,000 ÷ 1/100 is 100,000. And the prefix applies to the unit, not to the number's digits, so a value read in milligrams must be converted before it is compared with one in grams.
Taught in
Related terms
- exponent — An exponent states how many times a base is multiplied by itself, so 10³ means 10 × 10 × 10, and for a power of ten, each step moves the decimal point one place.
- decimal — A decimal writes a fraction using place value after a decimal point, so 0.75 means 75 hundredths, and the alignment of that point governs every operation.
Source: The math guides in this course (ratio and proportion, measurement and conversion, dosage calculation): every definition and worked value above was written for this course, because arithmetic and unit conversion are not a publisher's prose, and each guide shows the method worked. Elsevier's own HESI A2 page, which names math among the areas the exam covers, is the exam-side source. (Elsevier HESI A2 page accessed 2026-10-23; definitions written 2026-10-27)