phi

name

1. Abbreviation of Philadelphia.

noun

Etymology: From Late Latin phi, from Ancient Greek φεῖ (pheî).

1. Φ, the 21st letter of the Euclidean and modern Greek alphabet, usually romanized as "ph".
2. The golden ratio.
3. A visual illusion whereby a sequential pattern of lights produces a false sense of motion.

   “[…] tolerance (Frenkel-Brunswik 1949) for it showed that those persons with the strongest defences against internal conflict, i.e. obsessionals and conversion hysterics, were those least able to perceive the reality-conflicting phenomenon of phi.”

   “The illusion of movement in a highway construction sign is an instance of the phi phenomenon, which is also at work in motion pictures and television.”