Meaning of the word fi in English

What does fi mean in English? Explore the meaning, pronunciation, and specific usage of this word with Lingoland.

fi

US /faɪ/
UK /faɪ/

Noun

the 21st letter of the Greek alphabet (Φ, φ)

Example:
In mathematics, the symbol phi (φ) is often used to represent the golden ratio.
The physicist used the Greek letter phi in his equation.