|≈||approximately equal to|
|digits||indicates that digits repeat infinitely (e.g. 8.294 369 corresponds to 8.294 369 369 369 369 …)|
Femtogram or femtogramme is equal to 10-15 gram (unit of mass), comes from a combination of the metric prefix femto (f) with the gram (g). Plural name is femtograms.
A grain is a unit of measurement of mass, and, for the troy grain, equal to exactly 64.79891 milligrams. It is nominally based upon the mass of a single seed of a cereal.