Variables

• A particular element in a set is referenced by the name of the element, e.g., the element 55 in Naturals
• A general or generic element is referenced by a variable name or variable, e.g.

  n Î Naturals, name Î Students, city Î USCities, x Î Naturals

  we say: n is a variable over Naturals or the range of n is Naturals

• A variable can be assigned any value in its range, e.g.