ISI Standardization
The term micron and the symbol µ, representing the micrometre, were officially accepted between 1879 and 1967, but officially revoked by the ISI in 1967.
Nevertheless, in practice, "micron" remains a widely used term in preference to "micrometre" in many English-speaking countries, both in academic science (including geology, biology, physics, and astronomy) and in applied science and industry (including machining, the semiconductor industry, and plastics manufacturing).
Additionally in American English the use of "micron" helps differentiate the unit from the micrometer, a measuring device, because the unit's name in mainstream American spelling is a homograph of the device's name. The term "micron" is still extensively used in most English-speaking countries.
In engineering it is common to use the micron as a replacement for the traditional thou or mil, each of which represent a thousandth of an inch. 1 mil = 25.4 microns. So a trash bag may be originally specified as 0.35 mil thick, but stated as 8.89 microns.
"Micron" comes from Greek μικρόν (mikrón), which means "small".
Read more about this topic: Micrometre