photism

From the stem of Ancient Greek φῶς (phôs, “light”) +‎ -ism.

• (UK) IPA^(key): /ˈfəʊtɪzəm/

photism (plural photisms)

1. The color that a synesthete may report seeing in association with a particular letter or number.
2. (psychology) A luminous appearance, image or subjective perception of a hallucinatory nature.
   • 1902, William James, “Lecture X: Conversion—Concluded”, in The Varieties of Religious Experience: A Study in Human Nature […] , New York, N.Y.; London: Longmans, Green, and Co. […], →OCLC, page 251:

     I refer to hallucinatory or pseudo-hallucinatory luminous phenomena, photisms, to use the term of the psychologists.

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