Mole
Definition
The chemist's counting unit for enormous numbers of particles. One mole contains 6.022 x 10^23 particles, whether atoms, molecules, or ions.
Unit: mol
Technical definition
The mole (mol) is the SI base unit of amount of substance, defined as exactly 6.02214076 x 10^23 elementary entities. It links the microscopic particle scale to measurable macroscopic masses through molar mass.
Example
One mole of water, about 18 grams or roughly a tablespoon, contains 6.022 x 10^23 water molecules.
Common confusion
A mole counts things, it is not a mass. One mole of hydrogen atoms weighs about 1 gram while one mole of lead atoms weighs about 207 grams.