1.(Ympäristötieteet)lajin tai muun taksonin yksilömäärä pinta-ala- tai tilavuusyksikköä kohti
1.(chemistry) the ratio of the total mass of an element in the earth's crust to the total mass of the earth's crust; expressed as a percentage or in parts per million
2.(physics) the ratio of the number of atoms of a specific isotope of an element to the total number of isotopes present