[The coin] was in fact slightly larger than an 8,000-dollar Ankhian crown and the design on it was unfamiliar, but it spoke inside Hugh's mind in a language he understood perfectly. My current owner, it said, is in need of succor and assistance; why not give it to him, so you and me can go off somewhere and enjoy ourselves? (1.2.11)
There's a nonverbal language to everything we do. It has many attributes to it; the subconscious, body language, and the superego/id dichotomy are all examples. We can only say two things for certain: This aspect of language is extraordinary complex and mysterious, and it's usually pretty good for a laugh.
"How can a book tell a man what to say?" "I wish for an accommodation, a room, lodgings, the lodging house, full board, are your rooms clean, a room with a view, what is your rate for one night?" said Twoflower in one breath. Broadman looked at Hugh. The beggar shrugged. "He's got plenty of money," he said. (1.4.7-10)
The thing about language is that it's only natural so long as it's your language. Thankfully, Twoflower knows how to speak the universal language of cold-hard cash.
"At last!" he said. "My good sir! This is remarkable!" (Although in Trob the last word in fact became "a thing which may happen but once in the usable lifetime of a canoe hollowed diligently by ax and fire from the tallest diamondwood tree that grows in the noted diamonwood forests on the lower slopes of Mount Awayawa, home of the firegods or so it is said.") (1.4.34)
The hidden depths of the words we use everyday are truly extraordinary. Just take a glance at the etymology of most commons words. True, this example is exaggerated for laughs, but just barely.
"Yes, a great bunch of fellows, I thought—language was a bit of a problem, but they were so keen for me to join their party, they just wouldn't take no for an answer—really friendly people I thought…" Rincewind started to correct him, then realized he didn't know how to begin. (1.23.40-41)
We return to that nonverbal communication we talked about earlier, and this time we add cultural norms. When Twoflower says language was a bit of a problem, he means the words, but we see that it's also the cultural customs that are a bit beyond Twoflower's grasps. In other words, cultural customs are a type of language, too.
"I can see into your mind, false wizard! Am I not a dryad? Do you not know that what you belittle by the name tree is but the mere four-dimensional analogue of a whole multidimensional universe which—no, I can see you do not." (2.5.11)
Another example of the depths of words we don't consider in our day-to-day use of them. Sure, real trees might not serve as extra-dimensional housing for mythical creatures, but the word tree doesn't quiet do justice to the complex system of roots, leaves, trunk, xylem, and such that comprise that word. So cool.
The floor was a continuous mosaic of eight-sided tiles, the corridor walls were angled to give the corridors eight sides if the walls and ceilings were counted and, in those places where part of the masonry had fallen in, Twoflower noticed that even the stones themselves had eight sides. (2.8.4)
Yeah, you can't have a tiled floor composed entirely of regular octagons. You just can't do it, totally impossible. But language has the power to make the impossible possible, even if only in your mind for that brief moment before reality comes crashing back in on the fictional vortex.
Kring was saying form its temporary home in a tussock. "Some infidel was wearing an octiron collar, most unsporting, and of course I was a lot sharper in those days and my master used to use me to cut silk handkerchiefs in midair and—am I boring you?" "Huh? Oh, no, no, not at all. It's all very interesting," said Rincewind, with his eyes still on Hrun. (2.10.137-138)
The novel has a lot to say about how great language and communication is. But there is definitely a downside to language, and it often takes the form of other people and/or magical swords.
"How did you get in there?" said Twoflower. You summoned me, master. "I don't remember doing that." In your mind. You called me up, in your mind, thought the dragon, patiently. "You mean I just thought of you and there you were?" Yes. "It was magic." Yes. (3.13.16-23)
In the same way Twoflower's imagination conjures a dragon, this passage uses words to conjure a dragon in your mind. It's a pretty meta moment, which is fairly common in Discworld.
"It's rude to stare," said the [sea] troll. Its mouth opened with a little crest of foam, and shut again in exactly the same way that water closes over a stone. "Is it? Why?" asked Rincewind. How does he hold himself together, his mind screamed at him. Why doesn't he spill? (4.5.8-9)
We again witness the ability of language to conjure up the impossible. Rincewind's mind is screaming at us the whole time about how impossible it is, but did you even stop to consider your ability to imagine such an impossibility? Neither did we.
"All those worlds!" said Twoflower. "It's fantastic." (4.15.1)
If we consider Twoflower as the Discworld's surrogate for the reader, then we could just as easily read the worlds as stories. Like Twoflower, all readers enjoy boldly going where no man has gone before.