Evolution is both a fact and theory. This point is eloquently written about in an essay by Stephen Jay Gould entitiled "Evolution as Fact and Theory" (see: http://www.stephenjaygould.org/library/gould_fact-and-theory.html )
To quote from the essay (it's better to read the entire thing from the link, BTW):
In the American vernacular, "theory" often means "imperfect fact"part of a hierarchy of confidence running downhill from fact to theory to hypothesis to guess. Thus creationists can (and do) argue: evolution is "only" a theory, and intense debate now rages about many aspects of the theory. If evolution is less than a fact, and scientists can't even make up their minds about the theory, then what confidence can we have in it? Indeed, President Reagan echoed this argument before an evangelical group in Dallas when he said (in what I devoutly hope was campaign rhetoric): "Well, it is a theory. It is a scientific theory only, and it has in recent years been challenged in the world of sciencethat is, not believed in the scientific community to be as infallible as it once was."
Well, evolution is a theory. It is also a fact. And facts and theories are different things, not rungs in a hierarchy of increasing certainty. Facts are the world's data. Theories are structures of ideas that explain and interpret facts. Facts do not go away when scientists debate rival theories to explain them. Einstein's theory of gravitation replaced Newton's, but apples did not suspend themselves in mid-air, pending the outcome. And humans evolved from apelike ancestors whether they did so by Darwin's proposed mechanism or by some other, yet to be discovered.