From what I have observed, there are many different
varieties of parseltongue: “accents”, if you will. Three, however, emerge as
the most prominent types, and the ones that the average speaker of Parseltongue
might encounter in their lifetime. They are as follows:

Reptilian:

The first and most obvious type of Parseltongue, the
reptilian version of the language tends to be must shorter and less complex
than more developed styles. It tends to have little to no breaks in its
verbalization, most likely due to the difficulty for reptiles to adapt to human
patterns of speech. There are several subsets of this version of Parseltongue,
including Boa Reptilian, Venomous Reptilian, and others, though they all share
the same general traits.

Western:

The second type of Parseltongue, and the one which I will be
focusing my energy on in this book, is Western Parseltongue. This is the form
commonly utilized by humans, due to the more human-like speech patterns and the
additions of inflection and expanded vocabulary. This form is still understood
by reptiles, but some words may be difficult for them to comprehend, as they
are human concepts; it is also a form that is considered elitist to reptiles
and some humans, as it is used primarily by those humans who consider it an indication
of social status (such as the Gaunts, for instance). 

Western-Reptilian:

The final type of Parseltongue is Western-Reptilian, and
obviously this is a compilation of both the Western and Reptilian forms. It
does not have the complexity of the Western type, nor does it have quite the
fluidity of the Reptilian. It is a happy medium, most commonly used by those
witches and wizards who find that they have a natural talent for Parseltongue
but don’t often use it. Harry Potter was believed to have spoken
Western-Reptilian. 

From this point forward, it should be understood that I will
be proceeding with the Western form of Parseltongue unless otherwise stated.
Certainly, some basic concepts will be derived from the Reptilian version, but
it will not be a distinct focus.