micron(redirected from micra)
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Former term for micrometer.
micron (μ, mu)
Etymology: Gk, mikros, small
1 See micrometer, def. 2.
2 (in physical chemistry) a colloidal particle with a diameter between 0.2 and 10 μm.
micronA unit of length equal to 10–6 m.
Former term for the measurement now termed a micrometer.
An SI unit of length equal to one millionth of a metre (10−6 m). Symbol: μm. Syn. micron (obsolete term). See nanometre.
mi·cro·me·ter(mcm) (mīkrō-mētĕr, mī-kromĕ-tĕr)
1. One millionth of a meter; formerly called a micron.
2. A device for measuring various objects in an accurate and precise manner.
3. In medicine and biology, the term is usually used with reference to a glass slide or lens that is accurately marked for measuring microscopic forms.
[micro- + G. metron, measure]
n See micrometer.
pl. micra, microns [Gr.] micrometer; one thousandth (10−3) of a millimeter or one millionth (10−6) of a meter; abbreviated μm.