To begin to understand whether there is a difference in terms of "Mat" and "a curse". In Russian language there is quite an extensive amount of swear words, obscene, abusive, unprintable. Most of them was indecent and not always at the time had even the subtext of praise. Today, among the curses allocate a separate group, called obscene words.
Traditionally, Mat swear are the names of sexual organs and their parts, and the process of copulation. In addition, obscene considered all possible modified and smoothed form of these words. At the time, Dal, collecting material for his dictionary, does not emit foul language in a separate category in his records, they existed on a par with everyday expressions.
Following the definition of foul language, it should be noted that the word "bitch" is not obscene, it is just a name the sex of the dogs. Male - "male", female "bitch." Just as there is a division between "cat" and "cat", "ox" and "cow", "sheep" and "sheep".
Strictly speaking, this word is not even a dirty word, because these include the expression of disparaging, abusive, humiliating. The list can be found in special sections of the dictionary, but "bitch" was not found. Otherwise there also had to include the words: "goat", "horse", "pig" and many others.
But it happened, and the reasons for this can be a topic for a research that related to the word "bitch" is special. Moreover, the so-called person much more offensive than "dog" or "dog". That is why today there is a misconception that the term refers to abusive. Of course, at this stage of language development, it is not, though "bitch" may migrate into the category of obscene language, such examples already exist in history.
The preconditions for such a transition, there is fairly compelling. For example, can be found even in serious publications about the dog of the division of education, "Kobelkov" and "bitches" and "boys" and "girls" that is by definition wrong, because boys and girls are all the same people. Such reinsurance is called overcorrection, however, perceived this discrepancy adequately.
In this way, many of today's online edition of grammar and other language topics, speaking about the definition of the word "bitch" has already been used for two interpretations:
the female dog;
frivolous lustful woman (rude).

But even that in no way brings the word to the obscene.