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Vinony

femto-

prefix

  1. one quadrillionth
L739246 on Wikidata ↗

Wiktionary

prefix

Etymology: Etymology tree Proto-Indo-European *pénkʷe Proto-Germanic *fimf Proto-Indo-European *déḱm̥ Proto-Germanic *tehun Proto-Germanic *fimftehun Old Norse fimmtánder. Danish femtender. English femto- From Danish femten (“fifteen”), with reference to the (negative) exponent in the relevant power of ten; the same principle also explains atto-.

  1. In the International System of Units and other metric systems of units, multiplying the unit to which it is attached by 10⁻¹⁵ (short scale quadrillionth or long scale billiardth).