Evolution: Theory or Fact?

When Darwinists discuss evolution, the invariably speak about it as a fact.  They even say, "Evolution is a proven fact."  Textbooks and children's books also record evolutionary events with very definitive language, such as, "100 billion years ago, when dinosaurs evolved..."  When creationists discuss evolution, they invariably tag it with the word "theory".  So, which is it?

There is a wide range of belief about whether or not evolution is fact or theory, largely due to how one defines the term "evolution".  I looked it up in on wikipedia.org, but discovered that their definition neither separates out nor defines those proven elements of evolution from those which are theoretical.  They simply use the cryptic word "may" a lot.  This kind of smoke-screen, unfortunately, is typical when looking for answers about evolution and Darwinism.  

Paul Nelson, Ph. D., professor at Biola University and ID proponent, had this to say: "'Evolution' is a kind-of funny word.  It depends on how one defines it.  If it means simply 'change over time', even the most rock-ribbed fundamentalist knows that the history of the earth has changed--that there's been change over time.  If you define evolution precisely, though, to mean 'the common descent of all life on earth from a single ancestor via undirected mutations and natural selection'--that's textbook definition of neo-Darwinism, biologists of the first rank have real questions."

So, is evolution a fact or a theory?  The truthful, but also frustrating answer, would have to be 'both, on some level'.  That leads us to ask, "So, which parts of evolution are fact and which parts are theory?"

Two terms have arisen that help us understand this question.  They are "microevolution" and "macroevolution".  Microevolution is generally agreed on by scientists and non-scientists to be proven.  It is macroevolution, however, that gives everyone fits.

Microevolution:  "...the occurrence of small-scale changes in allele frequencies in a population, over a few generations, also known as change at or below the species level." (Wikipedia.org)

Macroevolution:   "...Macroevolutionary studies focus on change that occurs at or above the level of species...."  (Wikipedia.org) OR "Large-scale patterns and processes in the history of life, including the origins of novel organismal designs, evolutionary trends, adaptive radiations, and extinctions. Macroevolutionary research is based on phylogeny, the history of common descent among species."  (Answers.com)

I found a simpler definition of the terms on  (About.com) which is as follows: 

"Microevolution is used to refer to changes in the gene pool of a population over time which result in relatively small changes to the organisms in the population — changes which would not result in the newer organisms being considered as different species. Examples of such microevolutionary changes would include a change in a species’ coloring or size.

Macroevolution, in contrast, is used to refer to changes in organisms which are significant enough that, over time, the newer organisms would be considered an entirely new species. In other words, the new organisms would be unable to mate with their ancestors, assuming we were able to bring them together."

Term Trouble:

It must be noted that there is an overlap between these terms in that the level of "species" is not yet clearly understood by science.  Furthermore, it must be understood that the processes proven by science to cause microevolution are the same processes claimed by them to cause macroevolution.  Therefore, the processes themselves are proven to function to some degree. The question remains; however, as to how far those processes have effected the variety of species in existence today.