Psychosis =s some combination of delusions (grandiose, paranoid, somatic, bizarre, etc), disorganized thinking/speech (incoherent, loose associations, answers don't match questions, etc), hallucinations (auditory in particular), disorganized/abnormal behavior (agitation, inability to perform ADLs, ranging to catatonia), negative symptoms (decreased emotional expression, diminished speech output, lack of range in tone, no joy). Diagnosing underlying cause made by considering and ruling in/out non-psychiatric etiologies via careful history, exam, labs, testing and often observation over time.