Unit Definition (zettameter) The zettametre (or zettameter), symbol: Zm, is an SI metric unit of length. 1 zettametre is equal to 1e+21 metres, a very large distance. Not to be confused with a zeptometre.
Unit Definition (nanometer) Equal to 0.000000001 meters (formerly millimicron), or 0.03937 microinch.
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