phi

The 21st letter of the Greek alphabet.

The Greek letter φ, corresponding to the English ph .

The Greek letter φ, corresponding to the English ph .

The twenty-first letter of the Classical and Modern Greek, the twenty-second letter of Old and Ancient.

A visual illusion caused by lights turning on and off in a sequential pattern that implies motion.

The symbol for the golden ratio.

the 21st letter of the Greek alphabet