|Origin:||fallacia, from fallere 'to deceive'|
fal‧la‧cy plural fallacies
a false idea or belief, especially one that a lot of people believe is true [= misconception]:
It's a common fallacy that a neutered dog will become fat and lazy.
2 [uncountable and countable] formal
a weakness in someone's argument or ideas which is caused by a mistake in their thinking