1. 16th letter of the greek alphabet.
2. (Π). Symbol for osmotic pressure; in mathematics, symbol for the product of a series.
3. (π). Symbol for the ratio of the circumference of a circle to its diameter (approximately 3.14159265).
4. Symbol for inorganic orthophosphate (should not be used when covalently linked to another moiety).
5. The pH value for the isoelectric point of a given substance.
6. (Science: abbreviation) periodontal Index.