<prompt> Hallucinations areFeeling of familiarity with unfamiliar thingAlteration of perception of one realityMisinterpretation of stimuliPerception occurring without external stimulation  <response>: Hallucination A hallucination is a perception experienced in the absence of an external stimulus. The hallucinations can be in the auditory, visual, olfactory, gustatory or tactile domains. Auditory hallucinations are commonest types of hallucinations in non-organic psychiatric disorders. Ref: A Sho Textbook of Psychiatry, Niraj Ahuja, 7th Edition, pg. no. 13 