In regards to The Scarlet Letter, why does Hawthorne not tell us what the scarlet letter means as he does with many of his other color symbols?

It is in his
use of symbols in that Hawthorne has made one of the most significant
contributions to American literature.  Certainly, his novel is regarded by many as the first
symbolic novel to have been written in the United States.  In fact, it is Hawthorne's use of the
symbols of the scarlet A andthat have come to define symbolism as we know it:  A symbol means
what it is and more; it functions both literally and figuratively at the same time.  Thus, the
symbol is the richest and at the same time the most difficult of the literary devices.  For both
its richness and its difficulties result from its imprecision. It is this very imprecision which
Hawthorne has created with his two major symbols.  With this imprecision, his scarlet
A defines an area of meaning and interpretation that falls within that
allowed area.

The scarlet A takes on various appearances
and meanings as Hawthorne's narrative develops.  Of course, the first meaning of the
A is that of adultress...