The Seven SI Units: This figure displays the fundamental SI units and the combinations that lead to more complex units of measurement. It should be apparent that the move into modern times has greatly refined the conditions of measurement for each basic unit in the SI system, making the measurement of, for example, the luminous intensity of a light source a standard measurement in every laboratory in the world. A light source made to produce 20 cd will be the same regardless of whether it is made in the United States, in the UK, or anywhere else. The use of the SI system provides all scientists and engineers with a common language of measurement.