Definition: A millimeter (symbol: mm) is a unit of length in the metric system, equal to one-thousandth of a meter (0.001 m). It is commonly used to measure very small distances or thicknesses.

History/origin: The millimeter is part of the metric system, which was introduced in France in the late 18th century. The metric system was designed to create a universal, decimal-based system of measurement, and the millimeter emerged as a convenient subdivision of the meter.

Current use: Millimeters are widely used worldwide, especially in engineering, manufacturing, and design, where precision measurements are necessary. It is commonly used to measure thickness, small dimensions in mechanical parts, and in everyday contexts such as paper sizes and rainfall amounts.

Definition: A cup is a unit of volume commonly used in cooking to measure liquids and bulk foods. In the US customary system, one cup is equal to 8 fluid ounces or approximately 236.588 milliliters.

History/origin: The cup as a cooking measure originated from traditional household measurements. Its size and use vary internationally, but the US cup is widely standardized and used in American recipes. The cup's origin traces back to everyday household items used for measuring ingredients before metrication.

Current use: Cups are primarily used in cooking and baking to measure ingredients easily and consistently. While metric units are often preferred internationally, the cup remains common in American cookbooks, food packaging, and kitchen tools.