appearance the act of appearing in public view; "the rookie made a brief appearance in the first period"; "it was Bernhardt's last appearance in America"
performance any recognized accomplishment; "they admired his performance under stress"; "when Roger Maris powered four home runs in one game his performance merits awe"
An illusion is a distortion of the senses, revealing how the brain normally organizes and interprets sensory stimulation. While illusions distort reality, they are generally shared by most people. Illusions may occur with more of the human senses than vision, but visual illusions, optical illusions, are the most well known and understood.
OmegaWiki Dictionary
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illusion Deceptive or false appearance; that which misleads the eye or the mind.