The Greek letter pi for the ratio between circumference of a circle and its diameter was given only in the 18th century by William Jones, a mathematician (father of the more famous Sir William "Oriental" Jones, founder of Asiatick Society of Bengal), 2000 years after the Greeks had realized that such a thing existed. We, or at least some mathematicians, only celebrate March 14 (3-14) somewhat recently after the American usage of month followed by date (3-14), rather than the British usage of date followed by month (14-3).
Incidentally the ratio for circumference to diameter was stated as a Sanskrit sloka by Aryabhata in the fifth century. I attach the sloka and its meaning in this JPEG here. Aryabhata knew it was not an EXACT number but an approximate number ( though he didn't know about irrational or transcendental numbers), so he used the word "aassanow" which means "approximately".
If you liked this, you might also like reading these:
2. The mathematician Mahavira's Sanksrit Anthem for Mathematics
3. Nilakanta Somasatvan's Sloka - with a pun, a number, a date, a book
4. Some Sanskrit slokas from Indian Astronomy
5. VarahaMihira's Agastya Sthothram