‘Evolution is just a theory.’ What people usually mean when they say this is ‘Evolution is not proven fact, so it should not be promoted dogmatically.’ Therefore people should say that. The problem with using the word ‘theory’ in this case is that scientists use it to mean a well-substantiated explanation of data. This includes well-known ones such as Einstein’s Theory of Relativity and Newton’s Theory of Gravity, and lesser-known ones such as the Debye–Hückel Theory of electrolyte solutions and the Deryagin–Landau/Verwey–Overbeek (DLVO) theory of the stability of lyophobic sols, etc. It would be better to say that particles-to-people evolution is an unsubstantiated hypothesis or conjecture.
I know what people mean when they use the word "theory", I would simply say that it has varying definitions depending on the group using it.
It would be better to say that particles-to-people evolution is an unsubstantiated hypothesis or conjecture. - AIG
While it's true that AIG agrees that theory is different that belief. AIG agrees with me when I used the term "evolutionary beliefs" instead of "evolutionary theory". AIG doesn't belief evolution is a theory in the sense that it is well substantiated. However the definition that Wallcrawlr posted includes says "substantiated or widely accepted".
Evolution unfortuantely is widely accepted and thus a theory according to Wallcrawlr's posted definition. But only because it's widely believed.