漢字
Kanji are the
Chinese-derived
characters used in
the writing system of Japanese. The name literally means "
Han characters," and comes out in
Chinese as
hanzi, and in
Korean as
hanja.
To read kanji on your computer, all you need is Unicode support. Check out Using Unicode on E2 to find out how to get all the pretty characters in this writeup.
History
In the beginning, the Japanese had no writing system of their own. Kanji, in their archaic Chinese form, travelled to Japan over the fifth and sixth centuries, along with Buddhism, tea, and a host of other Far Eastern traditions. At first, the Japanese simply wrote all of their documents in Chinese, with each character representing a word. Soon, they developed another system where Japanese words were spelled out using the pronunciation of these Chinese characters without regard for their original meaning. Eventually, the latter system evolved into the simplified hiragana and katakana syllabaries, making it possible to write in a style more reflective of spoken Japanese without confusing Chinese people.
By the Meiji era, virtually all Japanese was written in a combination of kana and kanji, with kanji for the root words and hiragana or katakana for particles and conjugations. Educator Fukuzawa Yukichi was the first writer to make this method widespread.
After World War II, the educational reforms of the Allied Occupation of Japan completely changed the Japanese writing system. By then, upwards of four thousand kanji were appearing in daily newspapers, many of which were merely variations of one another: dictionaries listed over 50,000 characters! Literacy rates hovered around fifty percent.
Many kanji radicals were simplified (as happened to a greater extent in the PRC shortly afterward: only Taiwan continues to use the prewar style of kanji), and many characters were eliminated altogether. The Ministry of Education instituted a standardized list of 1,850 characters called the Toyo Kanji, which were to be the only characters approved for use in government publications and periodical literature. This list has since been expanded to 1,945 characters, and is now called the Joyo Kanji. 881 of these characters are called Kyoiku Kanji, and are taught to students in elementary school: they are the most important kanji, accounting for 90% of the written language and virtually all informal coorespondence.
Today, most computers are programmed to handle the JIS X 0208 set of kanji, which includes over 6,000 characters—the approximate vocabulary of Japanese literature students on a graduate level. Only 3,000 or so are used in modern writing, and it is entirely possible to read Japanese books with knowledge of only a thousand characters or so. Chinese writing uses about twice as many.
Non-Joyo kanji are usually presented with furigana next to them—little kana characters that tell you how the kanji is pronounced.
How Kanji Work
Kanji are descended from logographic writing, where the letters were written to look like what they represented. So we get 人 for "person," 田 for "rice paddy," and 木 for "tree." Others were drawn as arbitrary representations of rather complex ideas: 中 for "middle" is a good example.
These characters only account for about 10% of kanji, however. Most characters have a phonetic element, which indicates how the character is pronounced, and another element which indicates its meaning. These elements are called "radicals." The character 寺 ji, for instance, means "temple." Add the radical for "person," and you get 侍 shi "samurai." Add the radical for "day," and you get 時 ji "time."
This is a bit of an oversimplification, however. Most kanji have more than one pronunciation: usually, a kanji is assigned to both a native Japanese word and an imported Chinese pronunciation. Sometimes, a single kanji is used to represent several different Japanse words. Sometimes, a single kanji has two or more Chinese-derived pronunciations, indicating that it was used in loanwords from multiple eras where the character's Chinese pronunciation had changed. The only way to read most kanji is within context: otherwise, it can be difficult, if not impossible, to know how a character is supposed to be pronounced. Check out the kanji for "below" if you want to see a worst case scenario.
On the flip side, once you learn the radicals (there are about 200 in use today), it is possible to memorize kanji by their constituent parts. For example, the character for "like" (好) is a combination of "woman" (女) and "child" (子).
Kanji Styles
Most printed kanji are written in a style called kaisho, which originated in China late in the Han dynasty (around 200 AD). Inkan seals, postage stamps, money, and other official documents often use a much older style of kanji where the characters are squarer in appearance and far more intricate. There are also several levels of simplification used in Japanese calligraphy: the most common is the "grass hand" style that combines separate strokes into smooth curves. You can see some of these different styles at http://www2.gol.com/users/jpc/Japan/Kanji/history.htm.
To learn kanji
Start by learning calligraphy. It's artsy and can be incredibly tedious, but it will teach you how to form the strokes correctly, which is essential in writing legible characters, and helps immensely in remembering the radicals. This is what Japanese elementary school children do, and they are smarter than you, so get cracking.
Don't learn kanji in a linguistic void: memorize how kanji combinations are pronounced. Learn that 京浜 is Keihin, 京橋 is Kyobashi, and 下京 is Shimogyo: don't try to recite all the pronunciations of 京 in one sitting. Make flashcards. Give yourself writing quizzes.
Do all of this in Japan, if you can.