The definition of science poses some problems for people. Everyone seems to have an idea of what science is, but actually articulating it proves to be difficult. Doing so, however, is necessary to understand what science really is and what science is not. Understanding science is, in turn, necessary because of its incredible power and influence in modern society. Ignorance about science simply isn't a viable option.
The classical definition of science is simply the state of "knowing" - specifically theoretical knowledge as opposed the practical knowledge. In the Middle Ages the term "science" came to be used interchangeably with "arts," the word for such practical knowledge. Thus, "liberal arts" and "liberal sciences" meant basically the same thing.
Modern dictionaries are a bit more specific than that and offer a number of different ways in which the term science can be defined:
The observation, identification, desc<x>ription, experimental investigation, and theoretical explanation of phenomena. Methodological activity, discipline, or study An activity that appears to require study and method
For many purposes, these definitions can be adequate, but like so many other dictionary definitions of complex subjects, they are ultimately superficial and misleading. They only provide the barest minimum of information about the nature of science. As a consequence, the above definitions can be used to argue that even astrology or dowsing qualify as "science."
Distinguishing modern science from other endeavors requires focusing in particular on its methodology - the means by which it achieves results. Fundamentally, then, science can be characterized as a method of obtaining reliable - thought not infallible - knowledge about the universe around us. This knowledge includes both desc<x>riptions of what happens and explanations of why it happens.
The knowledge is reliable because it is continually tested and retested - much of science is heavily interdependent, which means that any test of any scientific idea entails testing other, related ideas at the same time. The knowledge is not infallible, because at no point do scientists assume that they have arrived at a final, definitive truth.