There are many different jokes centering around pi, most of which use puns in order to make the joke funny. An example of this is: "3.14% of sailors are Pi-rates." Other pi jokes use the question and answer response, such as "What is a math teacher's favourite dessert? Pi!" Some pi jokes are situational, as when a mathematician states the equation for area, "Pi R squared" and a baker responds with, "No! Pie are round, cakes are square!"
Pi is a mathematical constant represented by the Greek letter Pi. It is the ratio of a perfect circle's circumference to its diameter, and can be numerically approximated as 3.14159. Pi and pie are homonyms, meaning that they sound the same but are spelled differently. This relationship makes it easy to make jokes involving both words. Different professions use pi in different ways as well, making it easy to make jokes involving the many interpretations and uses of pi.
One good example is the following joke: "Several experts were all posed the following question: 'What is pi ?' The engineer said: 'It is approximately 3 and 1/7.' The physicist said: 'It is 3.14159.' The mathematician thought a bit, and replied 'It is equal to pi.' A nutritionist said: 'Pie is a healthy and delicious dessert!'"