Sciences can be divided into different kinds as thus:
Natural (physical), biological and social sciences: physics and chemistry are natural or physical sciences or sciences of nature; biology, zoology botany, and medicine are biological sciences or sciences of living beings; political science, economics, sociology, etc., are social sciences.
Exact and non-exact sciences: Exact sciences are mathematics, physics or chemistry, while non-exact sciences are die social sciences, including Political Science. A science is exact when its conclusions are verifiable. Results are precise and quantitative, and laws are universally valid. The results of the non exact sciences cannot be precise and quantitative, and their laws are not always and everywhere valid. Moreover, their variables are not measurable.
Descriptive and prescriptive or normative sciences: History is a descriptive science. Political Science is partly a descriptive science, and partly a nonnative science. Ethics is a normative science. Physical sciences are analytical, but not normative, sciences.
Idiographic and nomothetic sciences: An idiographic science deals with unique entities, such as the world system of States which are about 160 in number. Nomothetic sciences are concerned with general propositions or universal laws; e.g. physics or chemistry. But the more one describes an entity in details, the more he discovers regularities or laws in it. Hence the difference between die idiographic and nomothetic sciences is not of kind, but of degree.