1. the 21st letter of the Greek alphabet (Φ, φ)
2. the golden ratio, approximately 1.618, represented by the Greek letter φ
Usage: mathematics

Examples

• The Greek letter phi appears in many mathematical formulas.
• Students learned to write phi in their Greek alphabet lesson.
• The golden ratio phi is found throughout nature and art.
• Architects often use phi to create pleasing proportions.
• The Parthenon’s dimensions reflect the phi ratio.
• Phi equals approximately 1.618 in decimal form.