Q:

Say ABCDE is a pentagon. Is "ABCDE" the name of this pentagon?

This could be the start of a maths' exercise: "ABCDE is a pentagon."
In french, we would say "nom" (name) of the polygon to refer to "ABCDE", while "nature" of the polygon would refer to "pentagon".
Reading wikipedia, I figured out that, in english, "pentagon" is the name of this polygon. So, what is "ABCDE"? Is it possible to call it the name of the polygon, too, or is there any specific word?
Some context: I need a correct english word that I can use as a variable name in a software I develop, in order to store, for instance, the string "ABCDE" as a polygon's property whose name would be understood by anyone. For instance, if I write polygon.name, I guess anyone would guess it stores something like "triangle" or "pentagon" etc. Now it's about this "ABCDE": I cannot store it in polygon.name too. So, polygon.?????

A:

What is the area of pentagon ABCDE, assuming it is regular and the
  length of a side is 5cm?

There, "ABCDE" is the name of the pentagon. Notice that the name comes after the noun.
In your version

ABCDE is a pentagon.

setting aside all typographic issues and treating it as a verbal utterance, ABCDE is like a variable name, comparable to "Assume x is an odd number greater than 1000".  x is something of a name, a label.

