Noun

1. The irrational number (approximately 1·618), usually denoted by the Greek letter φ (phi), which is equal the sum of its own reciprocal and 1, or, equivalently, is such that the ratio of 1 to the number is equal to the ratio of its reciprocal to 1.

See also

• divine proportion
• extreme ratio
• golden cut
• golden mean
• golden number
• golden proportion
• golden section
• mean ratio
• sectio divina
• φ