# Definition:Amount of Substance/Units

## Definition

The SI unit of measurement of **amount of substance** is the **mole** $\mathrm {mol}$.

The CGS unit of measurement of **amount of substance** is the **gram-mole** $\mathrm {g \, mol}$.

The FPS unit of measurement of **amount of substance** is the **pound-mole** $\mathrm {lb \, mol}$.

### Mole

The **mole** is the SI base unit of **amount of substance**.

It is defined as exactly **Avogadro's number** of particles, that is, $6 \cdotp 02214 076 \times 10^{23}$.

### Gram-Mole

The **gram-mole** is the CGS unit of **amount of substance**.

It is defined as the number of atoms in $12$ grams of carbon-$12$.

### Kilogram-Mole

The **kilogram-mole** is an MKS unit of **amount of substance**.

It is defined as the number of atoms in $12$ kilograms of carbon-$12$.

### Pound-Mole

The **pound-mole** is the FPS unit of **amount of substance**.

It is defined as the number of atoms in $12$ pounds avoirdupois of carbon-$12$.