Implicit Set Definition/Examples/Letters of the Alphabet

Example of Implicit Set Definition
An example in natural language of implicit set definition is:
 * $S := \set {A, B, C, D, \dotsc, Z}$

That is, $S$ is the set of capital letters of the alphabet.

This definition is actually ambiguous, as it is not made clear exactly which alphabet is under consideration here.

The English one is assumed by context.