Phi – Φ φ
Phi is the twenty-first letter of the Greek alphabet. Its numerical value is 500. The appearance of Phi is unlike anything we have in the Latin alphabet. However, it may be an ancestor of the letter “P.” It features a circle and a line that crosses through it vertically.
This symbol represents a wide range of concepts in math and science. Some examples include the Golden Ratio, Euler’s totient function, the Veblen function, the ratio of free energy, magnetic flux, and more. Thanks to the distinct look, the Phi letter also appears in logos.