Definition:Primitive Symbol

Let $$\mathcal{A}$$ be the alphabet of a formal language $$\mathcal{F}$$.

The symbols which comprise $$\mathcal{A}$$ are called the primitive symbols of $$\mathcal{A}$$.

It is usual, during the development of a formal system to introduce further symbols in order to abbreviate what would otherwise be unwieldy constructions.

Hence the distinction between these newly-introduced symbols and the primitive symbols.