femtometre

noun

1. An SI unit of length equal to 10⁻¹⁵ metres. Symbol: fm

   “Holonyms: picometre < nanometre < micrometre < millimetre < centimetre < decimetre < metre < kilometre < megametre < gigametre < terametre < petametre < exametre < zettametre < yottametre < ronnametre < quettametre”

   “Meronyms: yoctometre < zeptometre < attometre”

   “The speed of light is about 0.3 femtometres per yoctosecond.”