The prefix "milli-" is a metric unit that denotes one-thousandth of a base unit. For example, in the metric system, one millimeter (mm) is equal to one-thousandth of a meter. This prefix is commonly used in various scientific and everyday measurements, making it easier to express small quantities. In addition to length, "milli-" is used in other measurements, such as milliliters (mL) for volume and milligrams (mg) for mass. These units help provide precise measurements in fields like chemistry, medicine, and cooking, where accuracy is essential for successful outcomes.