Intra-species adaptation is observable and replicable, even within a single specimen during its life cycle; the rest is not.
By scientific definition a confirmed observation is a fact.
Similarly, falsifiable explanations are called hypotheses and a confirmed hypothesis is a scientific theory.
Evolution is a confirmed hypothesis = theory, based on the entirely reasonable explanation that if you multiply "intra-species adaption" times, say, a million, the result is evolution of species.