See Also:

pi(2) (iou)



pi noun1. LME.
[Greek: in sense 2 repr. initial letter of Greek periphereia, English periphery, etc.; in sense 3 from the shape; in sense 4 after pi-orbital etc. (see P, P III).]
The sixteenth letter (, ) of the Greek alphabet. LME.
Math. The ratio of the circumference of a circle to its diameter, an irrational number equal to 3.14159...(approximated by 22 / 7). Usu. written . E18.
Electricity. A four-terminal set of three circuit elements in which one element is in series between two in parallel. Usu. attrib., as pi-network etc. Usu. written or . E20.
Physics & Chemistry. Used attrib. to designate an electron, orbital, molecular state, etc., possessing one unit of angular momentum about an internuclear axis. (Usu. written with ref. to one electron or orbital, with ref. to a molecule as a whole.) E20.
Comb.: pi-bond Chemistry a bond formed by a pi-orbital.