Fa is the twentieth letter of the modern Arabic order and the seventeenth of the older abjad order, from which it takes the numeral value eighty. It is written as a small closed loop with a tail running along the line, carrying a single dot above, and it joins on both sides, keeping the loop and shortening the tail when it does. It is a moon letter, so the lam of the definite article is pronounced before it.
Its sound is the voiceless labiodental fricative, the f of English. Arabic has no p, and words borrowed from languages that do have one are normally spelled with fa, which is why European place names and personal names appear in Arabic with an f where a p is expected. Persian and Urdu, written in the same script, added a letter for p by giving the ba skeleton three dots below.
Its name descends from the Northwest Semitic pe, the cognate of Hebrew pe and Syriac pe, whose sense was mouth, and it holds the numeral value eighty that Hebrew pe holds. The correspondence of names, positions and values is exact here, which is not true of every letter.
Fa is one of the two letters whose pointing differs between the eastern and western traditions of Arabic writing, and it is the clearer of the two cases. In the classical hands of the Maghreb and of al-Andalus, fa carries a single dot below the loop rather than above it.