A chain is a unit of length used in some older systems of measurement, particularly in surveying and land measurement. In the United States, one chain is equal to 66 feet or 22 yards. Internationally, it's defined as exactly 20.1168 meters.
Chains were historically used for measuring large plots of land and for surveying purposes, often in agriculture and real estate. However, the use of the chain as a standard unit of measurement has largely been replaced by the more modern and standardized metric and imperial systems, which use units like meters, feet, and yards.
The term "chain" comes from the practice of physically measuring land using a chain made of linked metal bars or wire. Each chain was typically 66 feet long, and surveyors would lay out chains end to end to measure distances across large areas. Today, modern surveying equipment such as electronic distance measuring devices (EDMs) and GPS technology have largely replaced the use of physical chains in land surveying.
The term "micron" is a unit of measurement used to express lengths or distances, particularly in the fields of science, engineering, and manufacturing. It is a unit of length in the metric system and is equal to one millionth of a meter, or 0.000001 meters. The symbol for the micron is "µm," where the Greek letter "mu" (µ) represents "micro," indicating that it is a very small unit of measurement.
Microns are commonly used to measure things at a microscopic level, such as the size of cells, particles, or features on a microchip. It's also used in various industries for precision measurements and quality control, particularly in fields like electronics, optics, and materials science. In some contexts, microns may also be referred to as micrometers.