Pi (letter)

The Pi (Greek neuter Πι, Π majuscule, minuscule π ) is the 16th letter of the Greek alphabet.

In its use as a numeral with the Greeks of the letter after the Milesian principle the value 80 had (see: Greek numbers).


The variant form of the minuscule π (or ) was the usual notation for the Byzantines. They can also be found in the earliest printing. Both forms, and, since the Middle Ages were next to each other in use even today is used in Greek script fonts when printed letter, it is gone from the normal Greek script. Today, its application is limited to mathematics, physics, astronomy and technology and there it represents a character by


  • In biology, π denotes an osmotic potential.
  • In physics, called π a meson, see Pion,
  • A stress tensor.
  • Denotes the wave number,
  • Is often used as a symbol for permutations,
  • Called the lemniscate constant ( as an analogue to the circle ),
  • Identifies the product sign Π the multiplication of several mathematical objects,
  • Referred to (x ) the prime function.


  • Pythagoras ( Πυθαγόρας )
  • Πάντα ῥεῖ ουδὲν, μένει. ( Panta Rhei, uden menei. "Everything flows, nothing remains. " )
  • Plato ( Πλάτων, Plato )
  • Protagoras ( Πρωταγόρας )


In Mac OS, the input is sufficient alt p or alt P.