The International System of Units (SI) defines seven base units: metre (for length), kilogram (for mass), second (for time), ampere (for electric current), Kelvin (for thermodynamic temperature), mole (for amount of substance), and candela (for luminous intensity). Joule is a derived unit of energy or work, defined as $\text{kg} \cdot \text{m}^2 \cdot \text{s}^{-2}$.