is the use of a specialized gland.

In D&D, the present accepted explanation is that this gland (located attached to the heart) is able to accumulate the various energies of the body and food stuffs (perhaps why dragons are known to eat some of their treasures?) and then channel this accumulated energy into the respiratory system, unleashing it as the breath weapon. Obviously, in our world where we don't have these kinds of elemental energies, this wouldn't work. But within the confines of Forgotten Realms physics, where "magic" is its own element, it makes PERFECT sense.

Another popular theory is that the specialized gland is an altered "venom" type gland that produces a flammable substance that can be ignited by flint/iron/similar pieces stored in the mouth on a temporary or permanent basis, perhaps in some sort of manipulative pouch. I believe I also read a couple theories that they actually possess TWO specialized glands that secrete substances that, when combined in the oral cavity, burst into a fire that could be forcibly expelled.

Then you have examples like in Anne McCaffery's Pern universe, where the dragons are only able to breathe fire by ingesting a certain type of stone that causes a sort of digestive conflagration (that obviously does not injure the dragons), causing the dragons to, essentially, have controlled fire burps (which is so in-elegant when you think about it )

In the latter two examples, they're really more "spitting" fire than breathing it. but "Fire spitting dragon" just doesn't sound as epic, does it?

There are any number of ways that are definitely stretches, but still explainable or biologically imaginable.

As for their speech, I don't see why it shouldn't be POSSIBLE.As pointed out, if you grant dragons a human-like intelligence (if you do) and consider the mimic abilities of other animals, I don't see why they wouldn't be able to develop speech of some sort. Furthermore, some cosmologies explain this anyways. To use DnD dragons again (I know the most about those), they have a fully and complexly developed larynx. I suppose we could debate about the ability of their mouths to make sounds, but again, you have birds who can do it, why not dragons? Now, of course, if your dragons are little more than extra-cunning animals, it makes substantially less sense for them to speak. But if your dragons are Fantastical Magnificent Intelligent Dragons, it actually makes less sense for them NOT to speak some sort of language.


If you didn't notice, I really like these kinds of questions It's fun to take fantastical creatures and imagine either what animals caused that myth, or how such creatures could hypothetically exist in our world and how they would function.