Chains
Unit of length equal to 66 feet, used especially in the U.S. public land surveys. The original measuring instrument (Gunter's chain) was literally a chain consisting of 100 iron links, each 7.92 inches long. Steel-ribbon tapes began to supersede chains around 1900, but surveying tapes are often still called "chains" and measuring with a tape is often called "chaining". The chain is a convenient unit in cadastral surveys because 10 square chains equal 1 acre.
Parsecs
The parsec is a unit of length equivalent to around 20 trillion (20,000,000,000,000) miles, 31 trillion kilometres, or 206,264 times the distance from the earth to the sun.
A parsec is also equivalent to approximately 3.26 light years (the journey distance if you travelled at the speed of light for three years and three months).
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