The first use of a new term in a document usually warrants a definition tag, <dfn>.

The nearest parent of the <dfn> tag must also contain the definition/explanation for the term inside the definition tag. Definition tags can also be linked to a related list of terms elsewhere on the page or site.

<p>The definition element <def title="definition of term">term</def> is a common way of defining terms.</p>

Neat-O Hover your mouse over the terms to see their definitions expanded.

html define elements