HYPERTEXT is...

For the majority of people who've lived amongst personal computers over the last forty years, hypertext's definition is intuited to mean this: text that you click on.

And yes, that's one modality of hypertext. But the concept is broader and more general than that.

Ted Nelson coined the term "hypertext", and first defined it in this way:

"This is a generic term for texts (and combinations of texts with other materials) which, because of their structure, require automatic handling and display devices. The hypertext will typically be non-linear, branching, and large, with various options to the user."

Ted Nelson, "The Hypertext", 1965

But the more often cited "original definition" is this one, from his 1965 ACM paper:

"Let me introduce the word "hypertext" to mean a body of written or pictorial material interconnected in such a complex way that it could not conveniently be presented or represented on paper. It may contain summaries, or maps of its contents and their interrelations; it may contain annotations, additions and footnotes from scholars who have examined it."

Ted Nelson, "A File Structure for The Complex, The Changing and the Indeterminate", 1965

My own synthesis of the idea of hypertext, based chiefly on Nelson's work but informed by the developments of intervening decades is something like this: explicitly interconnected written or audiovisual material from various contributors, including the audience, that can be created, presented to, and manipulated by reader-authors in varied novel and personal ways.

My view is that hypertext, since the 1990s certainly, has been popularized as a presentation medium, but not as a medium for creation and study. Alph is my attempt to build a system for making and doing with hypertext, rather than just consuming.