Which of these is the unit for the amount of substance in the International System of Units?

The mole (symbol: mol) is the unit of measurement for amount of substance in the International System of Units (SI). A mole of a substance or a mole of particles is defined as containing exactly 6.02214076×10²³ particles, which may be atoms, molecules, ions, or electrons.

The current definition was adopted in November 2018 as one of the seven SI base units, revising the previous definition that specified one mole as the amount of substance in 12 grams of carbon-12, an isotope of carbon.

The number 6.02214076×10²³ (the Avogadro number) was chosen so that the mass of one mole of a chemical compound in grams is numerically equal, for most practical purposes, to the average mass of one molecule of the compound in daltons. Thus, for example, one mole of water contains 6.02214076×10²³ molecules, whose total mass is about 18.015 grams – and the mean mass of one molecule of water is about 18.015 daltons.