A semantic link is a typed link where the element itself provides meaningful information about the link (semantics). For instance, in XML, you might have a BookTitle element <BookTitle isbn="0812511816"/>. You can use the semantic information provided in the element (the ISBN number) to create a link from this element to an online bookseller. The link describes some external relationship or issue.

An example of a semantic link would be (any syntax expressing) "A is-mother-of B". Some other relations like "B is-child-of A" may be implied by it.

Such links are the basis of a semantic network. The Semantic Web is only one example of these.