phi
/faɪ/
Proposed by a contributor, not yet supported by evidence.
Also seen as: phis
Sense 1
Meaning · English
Φ, the 21st letter of the Euclidean and modern Greek alphabet, usually romanized as "ph".
Noun
Sources & notes
Adapted from English Wiktionary (CC BY-SA 4.0, retrieved 2026-08-01 via kaikki.org).
Sense 2
Meaning · English
The golden ratio.
Noun
Sources & notes
Adapted from English Wiktionary (CC BY-SA 4.0, retrieved 2026-08-01 via kaikki.org).
Common questions
What does “phi” mean?
Φ, the 21st letter of the Euclidean and modern Greek alphabet, usually romanized as "ph".
Is “phi” formal or informal?
No register label has been reviewed yet — treat it as neutral and check the usage notes above.