The Harper Encyclopedia of Science, Edited by James R. Newman

Science: An organized body of knowledge and opinion which is systematically supported by formal proofs or by observational evidence. The sciences may be divided into two categories: (1) mathematics and logic (e.g. algebra, analysis, mathematical logic, meta-mathematics, and the formal logic of natural languages), which are concerned with the analysis, elaboration, and proof of the principles that regulate the permissible operation within systems of symbols; and (2) the empirical or observational sciences, which are concerned with the description and explanation of phenomena discovered by sensory observation.

A body of knowledge is regarded as an empirical “science” insofar as it meets two conditions: (1) it must be the outcome of a particular method of inquiry; (2) it must conform to certain principles of organization.

The method of scientific inquiry may be broadly described as follows: Every scientific hypothesis is regarded as subject in principle to being disproved by observational evidence. If any hypothesis has consequences that can be shown to be false, then it must be rejected, i.e. either abandoned outright or reformulated so that the false consequences no longer follow. Every hypothesis must be supported by actual observational evidence. A hypothesis is regarded as highly confirmed only if it has some true deductive consequences that alternative hypotheses lack. The evidence for a hypothesis must be public. This means that the relevant observational and experimental situations which exhibit the phenomena to be explained must be repeatable, at least in principle. Moreover, the evidence derived from any such experiment must be observable by a large number of persons. Thus, an introspection cannot constitute scientific evidence, but an introspective report can.

Scientific knowledge must be so organized that the scientist needs relatively few concepts and hypotheses for describing a variety of types of phenomena. This is accomplished with the help of specially constructed concepts that are both comprehensive in application and suitable for stating general laws that apply to a variety of cases.

My Addendum:

During first quarter in college my psychology teacher gave the class I was in a description of science that impressed me so much it has stuck with me since. She described psychology as the discipline by which we explain, predict and control behavior. By generalizing, I think I can say then that science is the discipline by which we explain predict and control whatever subject matter is under consideration. For example, physics would be the discipline by which we explain, predict and control nature (physics being derived from the Greek word for nature). Chemistry would be the discipline by which we explain, predict and control chemicals and chemical interactions. It seems to me that a key concept is the control that science gives us over our world. This control helps us survive, thrive and prosper.