Quintessence
Etymology
From Medieval Latin quinta essentia, “fifth essence.” Ancient and medieval thinkers held that beyond the four earthly elements — earth, water, air, fire — lay a fifth, purer element composing the heavens. From that “highest, purest substance” came the modern sense of a thing’s most refined essence.
noun · /kwin-TESS-ens/
The purest, most concentrated essence of something.
What it names
The distilled core — not merely a good example but the very substance that makes a thing what it is, stripped of everything incidental.
Example
Her clean, unhurried prose was the quintessence of good editing: you never noticed the work.
Related idea
An epitome is an embodying example you can point at; quintessence is the underlying essence that the example manages to embody.