The symbol phi represents the golden ratio.

I'm going to PHI for the game tonight.

I need to schedule an appointment with my PHI.

There are many phis in the fraternity.

The Phi Betes are hosting a charity event next week.

My friend John is a Phi Bete.

He is a Phi Bete.

The phi phenomena are optical illusions that create the perception of motion.

The phi phenomenon is a visual illusion that occurs when two or more stationary objects are presented in quick succession, creating the perception of motion.

The phi-features of the nouns are marked for plural.