Greek phi symbol

In LaTeX, use \phi; a character picker works too.

This straight phi symbol is used mainly in mathematical and technical notation; the formula supplies the value it labels. In ordinary Greek words, φ is the usual letter form. Using ϕ can keep the two forms distinct when a technical document includes both.

A character picker can find it by its Unicode name or by entering U+03D5.

Where did the Greek phi letter come from?

Greek writers added phi while adapting the Phoenician alphabet. Early evidence places its use for an aspirated p—a p sound followed by a puff of breath—in the eighth century BCE.

Greek communities spoke dialects and used local alphabets, which did not all mark aspirated consonants the same way. Phi became a broadly shared solution; the Milesian alphabet became a common standard around 400 BCE. The letter's spoken sound later shifted toward f.

That history belongs to the Greek letter, not its later mathematical job: ϕ is a straight technical form of phi.