Phi (letter)

Phi (Φ φ) is the 21st letter of the Greek alphabet and has a numeric value of 500.

The lower-case letter φ is used as a symbol for:

• Euler's phi function φ(n)
• The golden mean.
• In physics and mathematics, the value of an angle.
• The work function.
• The empty set.
• In signal processing, the phase of a sinusoidal[?] signal.

The upper-case letter Φ is used as a symbol for:

• magnetic flux

See also other things named phi, Phi phenomenon.