φ

Etymology 1
Named after ("Phidias"), who supposedly used the golden ratio in his work, by mathematician Mark Barr.

Symbol

 * 1)  The golden ratio, an irrational number with a value of approximately 1.618033988 which expresses the relationship that the sum of two quantities is to the larger quantity as the larger is to the smaller.

Symbol

 * 1)  Euler's totient function, an arithmetic function that counts totatives

Etymology
Derived from its majuscule counterpart Φ.

Letter

 * 1) Lower-case phi, the 21st letter of the ancient Greek alphabet. It represented the voiceless aspirated bilabial plosive  and later the  . It is preceded by υ and followed by χ.

Derived terms
See also phi

Letter

 * 1) The lower case letter phi (φι), the 21st letter of the modern Greek alphabet.