Fact

As used in everyday language:
something that is known to exist (or to have existed) beyond any doubt; the undeniable truth about a phenomenon as opposed to speculations about it.

As used in psychological science:
something that is known to exist (or to have existed) beyond any reasonable doubt, as determined by a large amount of high-quality evidence; the probable truth about a phenomenon based on inferences from a large amount of high-quality evidence.