delusion
UK: dɪˈluːʒn | US: dɪˈluːʒn
n. a false belief or opinion, especially one held despite strong evidence against it
n. (psychiatry) a symptom of mental disorder involving persistent false beliefs
Derived from Latin deludere ("to mock, deceive"), combining de- (indicating reversal or negation) and ludere ("to play"). The word originally implied "playing someone false" or "mocking reality." By the 15th century, it evolved to denote persistent false beliefs, influenced by its use in theological and philosophical contexts. The suffix -ion nominalized the action into a state of being deceived.
His claim of being a millionaire was pure delusion.
The patient suffered from delusions of grandeur.
Propaganda can create mass delusion among populations.
She clung to the delusion that her ex-lover would return.
Scientists must guard against the delusion of confirmation bias.