Kanji (help·info) (漢字) are the Chinese characters that are used in the modern Japanese logographic writing system along with hiragana (ひらがな, 平仮名), katakana (カタカナ, 片仮名), Indo Arabic numerals, and the occasional use of the Latin alphabet (known as the Romanization of Japanese, or "Rōmaji"). The Japanese term kanji (漢字) literally means "Han characters".
Chinese characters first came to Japan on articles imported from China. An early instance of such an import was a gold seal given by the emperor of the Eastern Han Dynasty in 57 AD[1]. It is not clear when Japanese people started to gain a command of Classical Chinese by themselves. The first Japanese documents were probably written by Chinese immigrants. For example, the diplomatic correspondence from King Bu of Wa to Emperor Shun of the Liu Song Dynasty in 478 has been praised for its skillful use of allusion. Later, groups of people called fuhito were organized under the monarch to read and write Classical Chinese. From the 6th century onwards, Chinese documents written in Japan tended to show interference from Japanese, suggesting the wide acceptance of Chinese characters in Japan.
The Japanese language itself had no written form at the time kanji was introduced. Originally texts were written in the Chinese language and would have been read as such. Over time, however, a system known as kanbun (漢文) emerged, which involved using Chinese text with diacritical marks to allow Japanese speakers to restructure and read Chinese sentences, by changing word order and adding particles and verb endings, in accordance with the rules of Japanese grammar.
Chinese characters also came to be used to write Japanese words, resulting in the modern kana syllabaries. A writing system called man'yōgana (used in the ancient poetry anthology Man'yōshū) evolved that used a number of Chinese characters for their sound, rather than for their meaning. Man'yōgana written in cursive style evolved into hiragana, a writing system that was accessible to women (who were denied higher education). Major works of Heian era literature by women were written in hiragana. Katakana emerged via a parallel path: monastery students simplified man'yōgana to a single constituent element. Thus the two other writing systems, hiragana and katakana, referred to collectively as kana, are actually descended from kanji.
In modern Japanese, kanji are used to write parts of the language such as nouns, adjective stems, and verb stems, while hiragana are used to write inflected verb and adjective endings (okurigana), particles, native Japanese words, words where the kanji is considered too difficult to read or remember, and words in which the kanji is not on the government-sanctioned list of characters. Katakana are used for representing onomatopoeia, non-Japanese loanwords, the names of plants and animals (with exceptions), and for emphasis on certain words.
While kanji are essentially Chinese hanzi used to write Japanese, there are now significant differences between kanji and hanzi, including the use of characters created in Japan, characters that have been given different meanings in Japanese, and post World War II simplifications of the kanji.
Kokuji (国字, "national characters") are characters particular to Japan. Kokuji are also known as wasei kanji (和製漢字, "Chinese characters made in Japan"). There are hundreds of kokuji (see the kokuji - sci.lang.japan Frequently Asked Questions). Many are rarely used, but a number have become important additions to the written Japanese language. These include:
In addition to kokuji, there are kanji that have been given meanings in Japanese different from their original Chinese meanings. These kanji are not considered kokuji but are instead called kokkun (国訓) and include characters such as:
Because of the way they have been adopted into Japanese, a single kanji may be used to write one or more different words (or, in some cases, morphemes). From the point of view of the reader, kanji are said to have one or more different "readings". Deciding which reading is meant depends on context, intended meaning, use in compounds, and even location in the sentence. Some common kanji have ten or more possible readings. These readings are normally categorized as either on'yomi (literally, sound reading) or kun'yomi (literally, meaning reading).
The on'yomi (音読み), the Sino-Japanese reading, is the modern descendent of the Japanese approximation of the Chinese pronunciation of the character at the time it was introduced. Some kanji were introduced from different parts of China at different times, and so have multiple on'yomi, and often multiple meanings. Kanji invented in Japan would not normally be expected to have on'yomi, but there are exceptions, such as the character 働 "to work", which has the kun'yomi hataraku and the on'yomi dō, and 腺 "gland", which has only the on'yomi sen.