Heteronymy is a matter of more than two expressions. A typical example is the set of terms for the days of the week, the set of basic colour terms (for more on colour terms, see 10.4) or terms for kinds of animals, plants, vehicles, etc.

The untelephoned are likely to be single people or lone mothers...

MESSENGER successfully flew by Mercury yesterday, gaining a critical gravity assist that will enable it to enter orbit about Mercury in 2011.

Why don’t we dispense with the formalities. Please call me Al.