For geometry, these undefined terms might be something like a point or a line, which we still choose symbols for.

Most theories, probably all, start with a set of undefined terms.

Axioms: Statements about the undefined terms which we assume are true.

A better way to think of it is that an undefined term has no single meaning, but can have many different meanings.

As part of the axiom system, we assume that "point" and "line" are undefined terms.

By themselves, the undefined terms are not enough to identify the similarities between the interpretations.

With Quality as a central undefined term, reality is, in its essential nature, not static but dynamic.

They are the "undefined" terms whose relations to one another is the subject matter of geometry.

Such undefined terms were high stakes, invariably requiring more than usual payment.

Unfortunately, Europe is always outstanding in its unlimited use of undefined legal terms.