parsec

See 1 E+16 m for comparable lengths, and scientific notation for an explanation of the notation used in this article. The parsec (symbol pc) is a unit of length used in astronomy. The length of the parsec is based on the method of trigonometric parallax, one of the oldest methods for measuring the distances to stars.
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Noun
1. a unit of astronomical length based on the distance from Earth at which stellar parallax is 1 second of arc; equivalent to 3.262 light years
(synonym) secpar
(hypernym) astronomy unit

n. (Astronomy) parsec, 3.26 light-years

Extensible language with PL/I-like syntax, derived from PROTEUS. "PARSEC User's Manual", Bolt Beranek & Newman (Dec 1972).

The distance at which a star would have a parallax of one arc second . It is equivalent to 3.26 light years , 206,265 astronomical units or 30.9 x 1012 km.