illusion

illusion (http://definr.com/illusion)

     n 1: an erroneous mental representation [syn: semblance]
     2: something many people believe that is false; "they have the
        illusion that I am very wealthy" [syn: fantasy, phantasy,
         fancy]
     3: the act of deluding; deception by creating illusory ideas
        [syn: delusion, head game]
     4: an illusory feat; considered magical by naive observers
        [syn: magic trick, conjuring trick, trick, magic,
        legerdemain, deception]