Phi

//faɪ// name, noun

name, noun ·Uncommon ·Advanced level

Definitions

Noun
  1. 1
    Φ, the 21st letter of the Euclidean and modern Greek alphabet, usually romanized as "ph".
  2. 2
    Initialism of protected health information. abbreviation, alt-of, initialism, uncountable
  3. 3
    the 21st letter of the Greek alphabet wordnet
  4. 4
    The golden ratio.
  5. 5
    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."

Proper Noun
  1. 1
    Abbreviation of Philadelphia. abbreviation, alt-of

Synonyms

All synonyms
pi

Example

More examples

"[…] 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."

Etymology

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

Related phrases

phi phenomenonphi-featureeuclidean alphabetgolden ratiogreek alphabet

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Data sourced from Wiktionary, WordNet, CMU, and other open linguistic databases. Updated March 2026.