What is the SI unit of mass?

The SI unit of mass is the kilogram. This unit is part of the International System of Units (SI), which is the standard system of measurement used in science and engineering worldwide. The kilogram is defined based on the mass of the international prototype of the kilogram, which is a physical object kept at the International Bureau of Weights and Measures.

Other units like grams are commonly used for measuring smaller masses and are considered a subunit of kilograms, where 1 kilogram is equal to 1000 grams. However, in the context of the SI unit system, the kilogram is the base unit designated for mass.

Units such as newtons and lumens represent different physical quantities; newtons measure force, while lumens measure luminous flux. Therefore, these options do not pertain to the measurement of mass within the SI unit framework.