- A pure substance.
- (physics) A hypothetical form of dark energy postulated to explain observations of an accelerating universe.
- A thing that is the most perfect example of its type; the most perfect embodiment of something.
- (alchemy) The fifth alchemical element, or essence, after earth, air, fire, and water
- The essence of a thing in its purest and most concentrated form.
- (transitive) To reduce to its purest and most concentrated essence.