Self: a self-referential meaning. That is inherent is the sense of the word itself. It is self-referential in the sense of a recursive acronym. For example, WINE. Wine represents, ‘WINE Is Not an Emulator’. The first letter of the first word represented by the acronym, is the acronym itself. In terms of meaning, this translates to defining self with self present—and key—in the definition.
Other words of a similar nature may be, ‘truth’, and ‘love’. Concept-constructs of that which can be imagined purely by itself, with no references or relations to other things or standards. In other words, of that that exist without necessary relation to others, being independent of context-dependent interpretation. Simply ‘selfly’—or ‘self-ful’. Words of this nature can have no exact opposites, like the number ‘0’ in a way.
Both self-referential in meaning and existence, self is a noun that admits no adjectival qualification. For instance, there can be no such thing as ‘good self’ or ‘bad self’. Self is self-contained: it is exactly what it is.