The Theory of Gravity.
Atomic Theory.
Germ Theory.
These are all theories, as well as facts.
Anyone who says that "evolution is just a theory" doesn't understand what a theory is.
To quote AronRa,
It is a fact that evolution happens; that biodiversity and complexity does increase, that both occur naturally only by evolutionary means.
It is a fact that alleles vary with increasing distinction in reproductive populations and that these are accelerated in genetically isolated groups.
It is a fact that natural selection, sexual selection, and genetic drift have all been proven to have predictable effect in guiding this variance.
It is a fact that significant beneficial mutations do occur and are inherited by descendant groups, and that multiple independent sets of biological markers exist to trace these lineages backwards over many generations.
It is a fact that birds are a subset of dinosaurs the same way humans are a subset of apes, primates, eutherian mammals, and vertebrate deuterostome animals.
It is a fact that the collective genome of all animals has been traced to its most basal form, and that those forms are also indicated by comparative morphology, physiology, and embryological development.
It is a fact that everything on earth has definite relatives either living nearby or evident in the fossil record.
It is a fact that the fossil record holds hundreds of definitely transitional species even according to it’s strictest definition, and that both microevolution and macroevolution have been directly-observed.
Evolution is a fact.
Atomic Theory.
Germ Theory.
These are all theories, as well as facts.
Anyone who says that "evolution is just a theory" doesn't understand what a theory is.
To quote AronRa,
It is a fact that evolution happens; that biodiversity and complexity does increase, that both occur naturally only by evolutionary means.
It is a fact that alleles vary with increasing distinction in reproductive populations and that these are accelerated in genetically isolated groups.
It is a fact that natural selection, sexual selection, and genetic drift have all been proven to have predictable effect in guiding this variance.
It is a fact that significant beneficial mutations do occur and are inherited by descendant groups, and that multiple independent sets of biological markers exist to trace these lineages backwards over many generations.
It is a fact that birds are a subset of dinosaurs the same way humans are a subset of apes, primates, eutherian mammals, and vertebrate deuterostome animals.
It is a fact that the collective genome of all animals has been traced to its most basal form, and that those forms are also indicated by comparative morphology, physiology, and embryological development.
It is a fact that everything on earth has definite relatives either living nearby or evident in the fossil record.
It is a fact that the fossil record holds hundreds of definitely transitional species even according to it’s strictest definition, and that both microevolution and macroevolution have been directly-observed.
Evolution is a fact.