pi

Meanings

1. The sixteenth letter of the Classical and Modern Greek alphabets and the seventeenth in Old Greek.
2. An irrational and transcendental constant representing the ratio of the circumference of a Euclidean circle to its diameter; approximately 3.14159265.

1. Metal type that has been spilled, mixed together, or disordered.

1. To spill or mix printing type.

1. Not part of the usual font character set; especially, non-Roman type or symbols as opposed to standard alphanumeric Roman type.

1. pica (conventionally, 12 points = 1 pica, 6 picas = 1 inch).
2. Piaster.

1. Pious.

1. Abbreviation of Piauí: a state of Brazil.
2. Initialism of Prison Industries, the prison-run work program for inmates.
3. Initialism of Philippine Islands.

1. Initialism of politically incorrect (see PC).

1. Initialism of processing instruction.
2. Initialism of partial induction (see AI).
3. Initialism of personal injury.
4. Initialism of principal investigator (“lead researcher on a grant-funded project”).
5. Initialism of private investigator.
6. Initialism of parallel import.
7. Abbreviation of phosphatidylinositol, a phospholipid component of eukaryotic cell membranes, also abbreviated in PtdIns.
8. Initialism of protease inhibitor.
9. Initialism of polyimide.
10. Initialism of ponderal index.
11. Initialism of penile inversion.
12. Initialism of power integrity.

1. A county of Chengdu, Sichuan, China.

Etymology

From Koine Greek πῖ (pî), from Ancient Greek πεῖ (peî), ultimately from Proto-Semitic *pay- (“mouth”). Doublet of pe. Its mathematical use apparently stems from its use as the first letter in περιφέρεια (periphéreia, “periphery; circumference”) and was first cited in 1706 in the Synopsis Palmariorum Matheseos by William Jones.