This is an essay.
It contains the advice or opinions of one or more Wikipedia contributors. This page is not an encyclopedia article, nor is it one of Wikipedia's policies or guidelines, as it has not been thoroughly vetted by the community. Some essays represent widespread norms; others only represent minority viewpoints.
The best definition of a grapefruit is a grapefruit. Not a photo of a grapefruit, a botanical, chemical, or physical description of a grapefruit; not a list of places where grapefruits are grown or foods that may be combined with them—but the actual item. Just as it is easier to learn through experience, so it is better to put a grapefruit into the hand of the student than to hold one up for examination; and better to allow the student to cut open the fruit and eat it than merely to stare at it or describe it.
We editors should avoid mere technical definition and hierarchical classification. In some cases, of course, the concept is purely abstract; in other cases, it's difficult to reach the reader with the item itself. Our article for grapefruit cannot put a grapefruit into the hands of readers, much less allow them to sample its taste and aroma—but the photo shown on that page is worth all of the words put together. It provides the reader a visual that answers the questions: "What really is a grapefruit? What is the 'grapefruit' that I see?"
Whenever possible, offer the reader the actual item or an example of it. This is quite possible in many cases. Flat file database discusses an abstraction, but demonstrates an actual flat file database; it puts one at his immediate disposal. If this is impossible or impractical, try to touch base with the reader as much as possible by reducing jargon and explaining arcane or difficult subjects in simple, clear terms. While it is eminently satisfying to the expert to be able to define a term exactly, it is more useful to the reader to be given a concrete example.