What does joule mean?
A joule is the SI unit of energy and work. It measures the amount of energy transferred when a force of one newton moves an object one metre, and it is also used for quantities such as heat and electrical energy. The unit is named after the English physicist James Prescott Joule, whose experiments established important relationships between heat, work, and mechanical motion. A joule is a very small amount of energy: ordinary human activity produces energy measured in thousands of joules, while larger quantities are commonly expressed in kilojoules or megajoules. The symbol J is widely used in scientific and technical contexts, and the abbreviated form watt, meaning joule per second, is especially common in discussions of power.
nounThe SI unit of energy or work, equal to the amount of energy used when a force of one newton acts through a distance of one metre. It is named after the English physicist James Prescott Joule.
- A unit of energy or work equal to the work done by a force of one newton acting through one metre.
"The scientist measured the energy transferred in the experiment and reported it in joules."
"A single battery may store several thousand joules of chemical energy."
"The device consumes about 20 joules of energy every second."
The plural is formed by adding -s; when abbreviated, the symbol J is normally unchanged.
"The experiment produced less than ten joules of heat."
The everyday unit of energy is named after James Prescott Joule, whose experiments helped establish the relationship between heat and mechanical work.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does joule come from?
The unit was named in honour of James Prescott Joule, the nineteenth-century English physicist noted for his measurements of mechanical work, heat, and energy. Its name follows the convention of deriving scientific units from prominent scientists, with the lowercase unit name and uppercase symbol J reflecting the SI system’s standards. The term belongs to the international vocabulary of measurement developed in the nineteenth and early twentieth centuries.
Related word forms
How joule is actually used
The plural is joules. The symbol for the unit is J, and the unit is usually used with SI prefixes such as kilojoule or megajoule when describing larger quantities.