Evolution, Gravity, Acidity... they are all theories, not "facts." Facts are things like: "when we measure weights on a balance, we find they are asserting approximately a force equal to their mass x what we think to be Earth's gravitational acceleration" or "when we put metal strips into hydrochloric acid, they dissolve at a rate consistent with what we believe HCl's pH to be"
Evolution is a theory, not a fact. It is a true theory.
Actually, the statement that evolution is a fact and not
a theory (and that Darwin's Theory of Natural Selection
best explains the fact) was made by Carl Sagan in one of
his books. It is confirmed by the the testimony of the
contemporary scientific community. (see the Nov. issue of
National Geographic for a good synopsis.) Essentially,
they are contending that evolution has independently been
empirically confirmed in studies of viruses, etc. And that
since Origin of Species was published (1859) there has
been such a massive array of data in support of evolution
that "theory" has become anachronistic. As always, terminology lags behind scientific actuality. We're
quibbling over semantics not scientific factuality.