[1] The Semitic Pê (mouth), as well as the Greek Π or π (Pi), and the Etruscan and Latin letters that developed from the former alphabet all symbolized /p/, a voiceless bilabial plosive.

A common digraph in English is ⟨ph⟩, which represents the sound /f/, and can be used to transliterate ⟨φ⟩ phi in loanwords from Greek.

In German, the digraph ⟨pf⟩ is common, representing a labial affricate /pf/.

Most English words beginning with ⟨p⟩ are of foreign origin, primarily French, Latin and Greek; these languages preserve the Proto-Indo-European initial *p. Native English cognates of such words often start with ⟨f⟩, since English is a Germanic language and thus has undergone Grimm's law; a native English word with an initial /p/ would reflect Proto-Indo-European initial *b, which is so rare that its existence as a phoneme is disputed.

In the International Phonetic Alphabet, ⟨p⟩ is used to represent the voiceless bilabial plosive.