Pi

Part of speech: noun, adjective

Definitions

1. The ratio of a circle's circumference to its diameter ; the sixteenth letter of the Greek alphabet ; disordered, jumbled printing type ; informally, excessively pious
2. A constant of roughly 3.14 relating a circle's circumference to its diameter ; a Greek letter, the sixteenth in the alphabet ; type scattered in a jumble during printing ; describing a person who is overly devout, in casual speech
3. The circle ratio of about 3.14159 ; the Greek letter written as a capital Π ; a heap of mixed-up loose type in a print shop ; an informal word for someone sanctimoniously religious

Etymology: The Greek letter pi takes its name from the Greek word for "periphery," and its mathematical career began with a quirk of that name. The symbol is the first letter of "periphereia," meaning circumference, and the ratio of a circle's circumference to its diameter came to be written with it. The first recorded use of the symbol in this sense appears in 1706, in the "Synopsis Palmariorum Matheseos" by William Jones, a Welsh mathematician who was one of the first to use it this way. The word pi as a term for printing type that has become jumbled is a separate matter. Its origin is unclear: it may come from the Greek letter used as a common example of a non-alphabetic character, from "pica," a type size, or from "pie" or "pied," meaning mixed or multicoloured, describing a jumbled heap of type. Each of these explanations has some support, and none is settled.