micron

Etymology 1

From French micron, from Ancient Greek μικρόν (mikrón), neuter of μικρός (mikrós, “small”).

noun

1. (physics) The thousandth part of one millimeter; the millionth part of a meter.
   2009, Jonathan Amos, (bbc.co.uk) Satellites weigh California water As one spacecraft lurches and drags through the Earth's uneven gravity field, the second follows 210 km behind, measuring changes in their separation to the nearest micron (a thousandth of a millimetre).
2. (figurative) A very tiny amount.

Etymology 2

From Ancient Greek μικρόν (mikrón), neuter of μικρός (mikrós, “small”).

noun

1. (linguistics) Synonym of breve