Energy
EN-er-jee
/ˈɛnərdʒi/
The capacity or ability to do work or produce change.
Energy exists in many forms (kinetic, potential, thermal, chemical, electrical, nuclear, etc.) and can be converted from one form to another, but it cannot be created or destroyed (Law of Conservation of Energy).
The story behind the word. "Energy" comes from the Greek word "energeia," meaning "activity, operation." It combines "en-" (in, within) and "ergon" (work). So, it literally means "in work" or "at work," perfectly capturing its modern scientific definition as the capacity to do work.
Word relationships
- power: "Power" is the rate at which energy is used or transferred, while "energy" is the capacity itself.
- vigor: "Vigor" refers to physical strength and good health, a more biological or personal sense of energy.
- lethargy: A state of sluggishness and lack of energy.
- inertia (metaphorical): Lack of activity or resistance to change, often due to lack of energy.
Commonly confused with
- Force: Energy is the capacity to do work; force is a push or pull.
Word family
- energetic (adjective): Having or showing a lot of energy.
- energize (verb): To give energy to.
Collocations
- kinetic energy
- potential energy
- renewable energy
- nuclear energy
- conserve energy
Idioms & expressions
- full of energy
- burst of energy
- save energy
Example sentences
- "Solar panels convert sunlight into electrical energy." Discussing renewable resources.
- "Energy cannot be created or destroyed, but it can be transformed from one form to another." From a scientific principle. (Law of Conservation of Energy)
Memory hook
The sun's ENERGY helps plants GROW and WORK. Grow Work Energy
When not to use
While "energy" is often used broadly (e.g., "I have no energy today"), in scientific contexts, it refers to the precise physical quantity.
Fun facts
- The SI unit for energy is the Joule (J), named after James Prescott Joule.
- Einstein's famous equation E=mc² shows the equivalence of mass and energy.
Explore more words
capacity, renewable, metabolism, efficiency, hydroelectric, Renewable Energy
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