The kilogram (kg) is the base unit for mass in the metric system (also known as the International System of Units, or SI).

It's important to note that while the kilogram is the base unit for mass, it's not a *basic* metric unit. "Basic" usually refers to the fundamental units, like length (meter), time (second), and mass (kilogram).

So, the kilogram is a base unit for mass in the metric system, and it's also one of the fundamental units in the system.