Since words like those of the Chinese and Japanese languages are sybolic, and not spelt phoneticly, how do they know what new words sound like?
That’s a good question, but I have no clue whatsoever.
Off-hand guess.
First off, the Japanese have a couple of phoenetic alphabets.
Secondly, I’m fairly certain that in the once using characters, new words are usually formed by combining old characters. It seems one could simply pronounce the components, no?
Or maybe they use the phonetic language to spell out the sybolic one? 
I believe the Japanese have a phonetic alphabet called Katakana they use to borrow words or make new ones. But for native words, many of them Chinese loanwords from thousands of years ago, they use a symbolic character set they also borrowed from the Chinese. Interesting sidenote: While the Japanese have borrowed from the Chinese many times, the basic Japanese language has no living lingusitic near relatives. In fact, it is nearly ungroupable because it has apparently evolved on its own for so long it has mutated to the point where the only connections it has to other languages are very tenuous.
Certified Language Mechanic here. Somebody call? Ah, Japanese. Okay, let’s open the hood and have a look around.
Japanese uses three writing systems - at the same time. One system is called KANJI. This is borrowed from Chinese. Each character stands for a word/concept. Normal Japanese writing, such as newspapers and books for adults, is mostly kanji - it is used for native Japanese words, as well as words borrowed from Chinese.
Next, we have KATAKANA. This is a syllabic writing system - each character stands for a syllable. Words borrowed from other languages than Chinese will be written in katakana. In theory, though, any Japanese word, borrowed or not, can be written in katakana. Books for small children, and textbooks for foreigners learning Japanese, will consist mostly of katakana.
And third we have HIRAGANA, which isn’t so important for what we’re talking about; it’s used for various grammatical markers, equivalent to affixes like un-, -ing, plural -s and possessive -'s in English.
So, if you mean “a new word” as in “a word that only recently entered the Japanese language”, the answer is that a Japanese reader would know how to pronounce it because it would be written in katakana. If you mean “a new word” as in “a word that someone has not encountered before”, then the answer is that if you learn to read Japanese, you have to memorize the kanji one at a time. Get down on your knees and thank the fates that your native language uses an alphabetic script.
China has started to use pin-yin, an alphabetic script based on the Latin/Roman alphabet (what we’re using right now), to help children learn to read.
Kanji may be considered symbolic characters, but for each Kanji there are only a few possible pronunciations. Most have only two common pronunciations - one that derives from the original Japanese language, and the other that is presumably based on the Chinese sound. Sometimes it’s not obvious which one is correct, but sometimes it is. In any case, when you see a word you haven’t heard before, it’s usually possible to make educated guesses.
As for completely new words (i.e. slang or technical terms), I think slang words usually enter the language as spoken words. New technical terms are usually made up of smaller words, so it’s obvious how it should sound like, the same way an English speaker knows how to pronounce “chlorofluorocarbon” or “magnetohydrodynamics.”
What is all this nonsense? Never mind about Japanese. How do English-speaking people know how to pronounce a new word? The answer is they don’t. In theory we are using a phonetic alphabet but it is borrowed from another language (latin) and it has been so messed up in the transition that it is hardly phonetic any more. So a dictionary needs to have a pronunciation guide which would be unnecessary if it were truly phonetical (as Spanish is).
Isn’t Korean in the same language group as Japanese?
Korean is. Chinese isn’t.
Yes, but how close is Korean? I was under the impression that Japanese is nearly isolated as far as living languages go.
Attempting to answer a couple questions:
I can’t give a whole lot of support to this claim, but I don’t believe Japanese and Korean are much alike at all.I admit, though, that I’m basing this only on my personal exposure to both, that being limited to one semester of HS Japanese and, well, hearing a fair amount of spoken Korean. My impression is that while they seem to be somewhat similar in terms of sounds and “rhythm,” (actual linguists, blast away) don’t really have that much in common. The written languages are also almost completely different; I’ve seen and heard that Korean also makes use of Chinese characters sometimes, but there doesn’t seem to be any real need for them, and I’m unclear as to exactly when and why they’re used. The written characters exclusive to Japanese and Korean aren’t related at all.
Chinese I know a little more about; new words (such as for new technology, etc.) will make use of existing characters as either phonetic devices (“ga fei” for instance, equals coffee, and has nothing to do with the meaning of the characters themselves) or to approximate what is meant. For instance, telephone is “dian hua” (electric… “speech?”) movie is “dian ying” (electric shadow") and many other devices are named this way. As for the creation of entirely new characters, I’m not really clear on if/how often this happens. Anyway, this isn’t gospel, I’m a first-year student and will humbly accept any corrections.
I’ve noticed that the Korean and Japanese written languages are very different. Korean is more circles and straight lines, while Japanese is curved lines and open figures. Both are distinctive. I can’t read a character of either. Nor can I speak them.
Korean has a distinct alphabet, Hangul, consisting of 14 primary vowel and 10 primary consonant sounds. It is syllabic, each “symbol” is actually a syllable which form words and sentences. It doesn’t resemble Japanese or Chinese. The Koreans use Japanese and Chinese characters in their written works, but it’s separate from Hangul.
Hangul is actually pretty easy to learn, its just the vocabulary and sentence structure that’s a little more difficult to pick up on.
Linguists are divided as to whether Korean and Japanese are related or not. One man’s proof is another man’s coincidence.
This linguist doesn’t know enough about the languages to form an opinion. But she can say she’s skeptical about claims that the two languages are distantly related to the Altaic family (a group which includes for instance Turkish), and finds theories proposing even further relationships to be downright bizarre.
Heard from a recent asian-studies conference that one of the new theories behind Japanese is that it is not derived from Korean proper but from proto-Koguryo (an old Korean Kingdom that was taken over by Silla by maybe 300 or so).
In Japanese newspapers, kid’s lit, etc, often next to the complicated kanji, in a smaller script in the margin they put a katakana/ hiragana phonetic equivilant to help people with the unfamiliar words (if that’s what the question is).
OK, as someone who’s studied Japanese on his own and spent a little time in Japan (and has some books to show for it), let me throw in my ¥.02:
The dictionaries I remember seeing had hiragana spellings after the kanji in the main entry. I seem to remember newspapers having the hiragana to the left of presumably unfamiliar kanji as well, in the margins between columns of text.
I have 10 out of a 12-booklet series of learning kanji for beginners that I bought while in Japan and they show the hiragana spellings as part of the process for memorizing it. So it seems, at least as my experience tells me, that it’s pretty easy for the Japanese to learn how a new kanji sounds - generally the opportunity is right there with it.
As for linguistic relations between Korean and Japanese, what I remember of my linguistics classes from college showed me that while the grammatical structures of the two were very similar, the vocabularies were entirely different - for example, the accusative particle o in Japanese had il as its counterpart in Korean.
This is just what I’m sure I know; it’s all pretty skimpy so the standard cum grano salis warning applies.
Call me pedantic, but…
It is interesting to note how often the word ‘borrowed’ crops up in this thread.
Since when have words ever been ‘borrowed’ from other languages? More to the point, will we ever be expected to give these ‘loan-words’ back?
[BTW, I’m being deliberately facetious here, just to make a point.]
Aaah, what would you know? You never spend any time in Japan actually learning the language or the culture, you just go around trashing Osaka and Tokyo. 
As Kyberneticist and Space Vampire have already pointed out, completely new words, such as “laser” or “the Internet,” are usually formed by combining two existing characters, so as long as one can pronounce the existing characters, one can pronounce the new word.
(By the way, awesome handles… The thought of a union of “Kyberneticist” and “Space Vampire” for some reason gives me the same goose bumps I got when I heard Frank Zappa mention in an interview that he and Alice Cooper used to get together on occasion. As my old college roommate put it at the time, “if there was ever a threat to national security…” :p)
However, I guess that the O.P. may have been referring to a Chinese or Japanese reader encountering a character that he or she has never seen before. In other words, how does a Chinese or Japanese twelve-year-old figure out how to pronounce a character that she has never seen before? That is a rather interesting question. Students probably memorize most characters under the guidance of their teachers and parents. When I started studying Chinese I asked some Chinese friends about this, and they were of the opinion that most learning is done through memorization in school. However, with experience, you can sometimes make an educated guess about the pronunciation of a character. Once you have mastered basic Chinese, you can often get a hint to the pronunciation of most unfamiliar characters. It is almost never enough of a lead for you to be certain, but it’s usually enough to make a guess. Some linguists (e.g., T.K. Ann in “Cracking the Chinese Puzzles”) have argued that this is what every Chinese unconsciously has been doing from childhood to adulthood. Complex Chinese characters are almost always made up of combinations of basic characters. There are about 170 basic characters, and these are used as components to form countless more complex characters. Quite often, one of the basic components in a character indicates the pronunciation and/or the tone of the complex character. Therefore, once you know the pronunciation of the basic characters, you may guess at the pronunciation of most complex characters.
For example, the basic character for “land” (pronounced “tu” with a falling and then rising tone) is used as a subcomponent of the characters for “spit”, “vomit”, “shut out”, and “belly”. These complex characters are pronounced “tu”, “tu”, “du”, and “du”, although with different tones.
Of course, this is for Chinese. I have always been curious about how a Japanese would figure out how to pronounce an unfamiliar Chinese character. If I understand the previous posters correctly, Japanese have to see a katakana or hiragana transcription to make sense of an unfamiliar character? (Feel free to correct me if I have misunderstood.) And, it should be said that the introduction of simplified characters in mainland China is wrecking havoc with the method mentioned above, since the original subcomponents often have been edited out from the new, simplified characters.
My impression of what Amadeus meant by “new word” is one that a young reader is seeing in writing for the first time and has no way of knowing how it is pronounced without asking someone.