Lexia is a term often used by hypertext theorists to describe a minimal unit of reading, together with any attached links.
The term originates with the French literary theorist Roland Barthes in his "Introduction to the Structural Analysis of Narrative." For Barthes, a lexia can be as small as a single word, and can range through to sentence fragments, full sentences or even multi-line paragraphs.
Indeed lexia in this passage is autological, in that it is itself a minimal unit of reading with an attached link.
Much of hypertext today takes the form of passages of unlinked text surrounded by navigation links. Encountering these kinds of lexia, one receives the impression that the authors, who have dropped digitized versions of printed pages into an electronic environment, don't seem to grasp the defining qualities of hypermedia and use HTML chiefly as a text formatting system.