Pi: The Coptic Letter (Value 80), from Greek Pi

Pi is the seventeenth letter of the Coptic alphabet and carries the numeral value eighty, closing the tens before ro opens the hundreds. It writes the p sound, which Egyptian had possessed throughout its recorded history, so unlike gamma or zeta the letter went straight into native service and is among the most frequent consonants in the language. Its grammatical weight is what a reader notices first. Coptic marks a masculine singular noun as definite with an element built on pi, and the same letter appears in demonstratives, in possessive constructions and in a number of verbal prefixes, so it turns up in the opening lesson of every Coptic grammar and thereafter on every page. That definite article had a long afterlife outside Coptic. In many Egyptian words the article fused permanently to the noun, so that the compound became the ordinary name of the thing, and a great many Egyptian place names and personal names entered Greek in that fused form.

From Greek they passed into Latin and into modern European languages, which is why a family of names beginning with a p syllable can be traced back through Coptic to an Egyptian noun with its article attached. Pi in the numeral series is worth eighty, and like every Greek derived letter of the Coptic alphabet it holds exactly the value it held in Greek, since Coptic borrowed the numeral series along with the letters rather than devising one of its own.