What is the base unit of mass in the International System of Units (SI)?

The base unit of mass in the International System of Units (SI) is the kilogram. This unit is fundamental because the SI system is designed to provide a standardized framework for measurement in science and engineering. The kilogram is defined based on a specific physical constant: it is equal to the mass of a specific prototype known as the International Prototype of the Kilogram, which was a physical object made from platinum-iridium.

While other units, such as the gram, pound, and ounce, are commonly used in various contexts, they are either derived from the kilogram or represent different measurement systems. The gram, for instance, is one-thousandth of a kilogram and is often used for smaller quantities. The pound and ounce are part of the imperial system of measurements rather than the SI system.

By using the kilogram as the base unit for mass, the SI system ensures consistency and universality across scientific disciplines, facilitating communication and reducing the likelihood of errors in measurement.