CGS system
The CGS (or cgs) system (or centimeter-gram-second) of units predated the current International System (also known as SI units), which is the current iteration of the metric system.
Although many fields, including most of the healthcare sciences have abandoned CGS for everyday work, there are still fields that employ them. Also, of course it is helpful to have knowledge of these legacy units when reading the older published literature.
The CGS system is a coherent system of units based on the fundamental units of centimeter for distance, gram for mass, and second for time. It was superseded by the MKS system, which was based on the fundamental units of meter for distance, kilogram for mass, and second for time.