Capital letters ∏:
Continuous product operator in mathematics
Lowercase letter π:
Mathematical constant pi (its value is about 3. 14, for more detailed values, please see the entry pi).
Function (mathematics) π(n) is the number of prime numbers not greater than n.
π mesons in particle physics
π bond, a chemical bond formed by overlapping atomic orbits side by side.
Profit in microeconomics
Inflation rate in economics
п in Cyrillic letters and p in Latin letters all come from pi.