fact fakt/Submit noun a thing that is known or proved to be true. "the most commonly known fact about hedgehogs is that they have fleas" synonyms: reality, actuality, certainty, factuality, certitude; More information used as evidence or as part of a report or news article. "even the most inventive journalism peters out without facts, and in this case there were no facts" synonyms: detail, piece of information, particular, item, specific, element, point, factor, feature, characteristic, respect, ingredient, attribute, circumstance, consideration, aspect, facet; More used to refer to a particular situation under discussion. noun: the fact that "despite the fact that I'm so tired, sleep is elusive"

prove pruːv/Submit verb past participle: proven 1. demonstrate the truth or existence of (something) by evidence or argument. "the concept is difficult to prove" synonyms: demonstrate, show, show beyond doubt, show to be true, manifest, produce/submit proof, produce/submit evidence, establish evidence, evince; More 2. demonstrate to be the specified thing by evidence or argument. "if they are proved guilty we won't trade with them"

A fact still has to be proven. "observing" it is the way in which it is proven.

Take einstein's theory of gravitational waves literally this year, proven now, because we detected them, exactly how we predicted.