The lowercase π everyone means by ‘the pi symbol,’ the capital Π that means ‘product’ in math, and the dedicated ∏ product operator — the notation William Jones introduced in 1706 and Leonhard Euler turned into the world standard. Click any symbol to copy it instantly.
Pi's lowercase glyph, π (U+03C0, GREEK SMALL LETTER PI), is one of the most recognizable characters in all of mathematics — the ratio of any circle's circumference to its diameter, roughly 3.14159 and running forever without repeating. What most people don't realize is that the symbol is far younger than the number: the Welsh mathematician William Jones first used π this way in his 1706 book ‘Synopsis Palmariorum Matheseos,’ borrowing the Greek letter that begins ‘periphery.’ For three decades it went nowhere — until Leonhard Euler, the most influential mathematician of the age, adopted it around 1737 and cemented it as the global standard through his 1748 ‘Introductio in analysin infinitorum.’ The capital form, Π (U+03A0), does entirely different work: in math it's the product operator, the multiplicative twin of Σ summation, and it has its own dedicated glyph, ∏ (U+220F, N-ARY PRODUCT). Pi is both irrational (proved by Lambert in 1761) and transcendental (Lindemann, 1882) — and it even gets its own holiday every March 14.
The Greek letter itself. The lowercase π is the famous math constant; the capital Π is a different tool entirely.
Capital Π is the product operator, and — exactly like sigma — it has a dedicated math glyph, ∏ (N-ARY PRODUCT), that is a separate Unicode character from the letter. It's the multiplicative mirror of ∑ summation, letter for letter.
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Product, summation, and the operators and Greek letters that fill out an equation.
Pi's operator twin: just as Π pairs with the ∏ product sign, Σ pairs with the ∑ summation sign.