The letter phi () is the twenty first letter of the Greek alphabet. It’s a unvoiced bilabial fricative, which signifies that it’s produced by forcing air by way of the lips with out vibration. The sound of phi is just like the sound of the letter “f” in English.
Phi is utilized in a wide range of phrases, together with “philosophy,” “physics,” and “phonetics.” It’s also used within the Greek numeral system, the place it represents the quantity 500.