mi·cron also mi·kron 
(mīkrŏn′)
(mīkrŏn′)n. pl. mi·crons or mi·cra (-krə) also mi·krons or mi·kra (-krə)
A unit of length equal to one thousandth (10-3) of a millimeter or one millionth (10-6) of a meter. Also called micrometer.
[From Greek mīkron, neuter of mīkros, small.]