Pi is a mathematical constant, the ratio of the circumference of a circle to its radius. Its value is rounded to 3.14159 and represented by the Greek letter π.
Its decimal value is infinite, having been calculated to over a million decimal places with no regular repeating pattern.
Pi in the Person of Interest Universe
- “2πR”: Finch impersonates a high school teacher to approach their next number, a teenager attending this school. He lectures to the class on how pi is assumed to contain any finite sequence of digits within its neverending decimal sequence, and stresses the fact that "now, whatever [they] do with this information, will be entirely up to [the student]".
- “Pretenders”: Elizabeth Bridges express how she loves Euler's identity, in which e, π, i, 1, 0 are used.
- “Point of Origin”: Dominic uses the same argument to make his point to a doubting head of the Trinitarios gang before having him executed by his own second-in-command.
- “The Cold War”: The entrance to the new underground base of operations of Team Machine is hidden behind an apparently abandoned vending machine. The passcode to the door is 3141.
- “Search and Destroy”: Root use the code of 314 to open the briefcase which contains a replica of the Fabergé Pine Cone Egg.
- “YHWH”: The Machine sends the code of 314 to Finch and Root in order to point them to the Briefcase which would later be used to save the core of the Machine.