1. The intrinsic or indispensable properties that serve to characterize or identify something.
2. The most important ingredient; the crucial element.
3. The inherent, unchanging nature of a thing or class of things.
a. An extract that has the fundamental properties of a substance in concentrated form.
b. Such an extract in a solution of alcohol.
c. A perfume or scent.
5. One that has or shows an abundance of a quality as if highly concentrated: a neighbor who is the essence of hospitality.
6. Something that exists, especially a spiritual or incorporeal entity.
[Middle English essencia and French essence, both from Latin essentia, from esse, to be, from the presumed present participle *essns, *essent- (on the model of differentia, difference, from differns, different-, present participle of differre, to differ), created to translate Greek ousi (from ousa, feminine present participle of einai, to be); see es- in Indo-European roots.]
Reality is an empty glass half-full of birds and bats who flutter with opinions about the blackness of space, the whiteness of stars, the beauty of feathers and the ugliness of nothing.