What is the term for a false belief that is strongly held despite evidence to the contrary?

The term for a false belief that is strongly held despite evidence to the contrary is delusion. Delusions are fixed beliefs that do not change even when presented with conflicting evidence. They are characteristic features of various mental disorders, particularly psychotic disorders such as schizophrenia or delusional disorder.

In the context of psychiatric diagnoses, a delusion is not merely an incorrect understanding or a flawed belief; it is a deeply entrenched conviction that the individual regards as an undeniable truth. This quality distinguishes delusions from other types of false beliefs or misconceptions, which may be more malleable and subject to reconsideration.

In contrast, hallucinations refer to sensory experiences that occur without any external stimulus, such as hearing voices or seeing things that aren't there. Illusions are misperceptions of real external stimuli, meaning they arise from actual sensory input but are misinterpreted. Myths, on the other hand, are widely held but unfounded beliefs or stories that may not necessarily pertain to an individual's psychological state and are often cultural or social in nature. Thus, delusion is the correct term for a strongly held false belief resistant to contrary evidence.