noun

a mistaken belief, especially one based on unsound arguments.

the notion that the camera never lies is a fallacy

misconception,mistaken belief,misbelief,delusion,false notion,mistaken impression,misapprehension,misjudgement,miscalculation,misinterpretation,misconstruction,error,mistake,untruth,inconsistency,illusion,myth,fantasy,deceit,deception,sophism,sophistry,casuistry,faulty reasoning,unsound argument