(noun) The inherent nature of a thing or idea.
"Every act of rebellion expresses a nostalgia for innocence and an appeal to the essence of being."
"The energy of the mind is the essence of life."
"The real glory is being knocked to your knees and then coming back. That's real glory. That's the essence of it."
"The Essence of Knowledge is, having it, to use it."
"The rose's rarest essence lives in the thorns."