Two commonly used systems of units are English units and SI units. Physics is about trying to find the simple laws that describe all natural phenomena

Scientists attempt to describe the world by formulating models, theories, and laws Systems of units are built up from a small number of base units, which are defined by accurate and precise measurements of conventionally chosen base quantities.

units — standards used for expressing and comparing measurements. base unit — standard for expressing the measurement of a base quantity within a particular system of units; defined by a particular procedure used to measure the corresponding base quantity. law — description, using concise language or a mathematical formula, of a generalized pattern in nature supported by scientific evidence and repeated experiments. physics — science concerned with describing the interactions of energy, matter, space, and time; especially interested in what fundamental mechanisms underlie every phenomenon.