Katakana in the context of "Hepburn romanization"

The Heian period (平安時代, Heian jidai) is the last division of classical Japanese history, running from 794 to 1185. It followed the Nara period, beginning when the 50th emperor, Emperor Kammu, moved the capital of Japan to Heian-kyō (modern Kyoto). Heian (平安) means 'peace' in Japanese. It is a period in Japanese history when the Chinese influences were in decline and the national culture matured. The Heian period is also considered the peak of the Japanese imperial court, noted for its art, especially poetry and literature. Two syllabaries unique to Japan, katakana and hiragana, emerged during this time. This gave rise to Japan's famous vernacular literature, with many of its texts written by court ladies who were not as educated in Chinese as their male counterparts.

Although the Imperial House of Japan had power on the surface, the real power was in the hands of the Fujiwara clan, a powerful aristocratic family who had intermarried with the imperial family; most Emperors of the Heian era had mothers from the Fujiwara family. The economy mostly existed through barter and trade due to the lack of a national currency, while the shōen system encouraged the growth of aristocratic estates that began gradually asserting their independence from Imperial control. Despite a lack of serious warfare or domestic strife during the Heian era, crime and banditry were widespread as the Emperors failed to police the country effectively.

The modern Japanese writing system uses a combination of logographic kanji, which are adopted Chinese characters, and syllabic kana. Kana itself consists of a pair of syllabaries: hiragana, used primarily for native or naturalized Japanese words and grammatical elements; and katakana, used primarily for foreign words and names, loanwords, onomatopoeia, scientific names, and sometimes for emphasis. Almost all written Japanese sentences contain a mixture of kanji and kana. Because of this mixture of scripts, in addition to a large inventory of kanji characters, the Japanese writing system is considered to be one of the most complicated currently in use.

Several thousand kanji characters are in regular use, which mostly originate from traditional Chinese characters. Others made in Japan are referred to as "Japanese kanji" (和製漢字, wasei kanji), also known as "[our] country's kanji" (国字, kokuji). Each character has an intrinsic meaning (or range of meanings), and most have more than one pronunciation, the choice of which depends on context. Japanese primary and secondary school students are required to learn 2,136 jōyō kanji as of 2010. The total number of kanji is well over 50,000, though this includes tens of thousands of characters only present in historical writings and never used in modern Japanese.

Kana (仮名; Japanese pronunciation: [ka.na]) are syllabaries used to write Japanese phonological units, morae. In current usage, kana most commonly refers to hiragana and katakana. It can also refer to their ancestor magana (真仮名; lit. 'true kana'), which were Chinese characters used phonetically to transcribe Japanese (e.g. man'yōgana); and hentaigana, which are historical variants of the now-standard hiragana.

Katakana, with a few additions, are also used to write Ainu. A number of systems exist to write the Ryūkyūan languages, in particular Okinawan, in hiragana. Taiwanese kana were used in Taiwanese Hokkien as ruby text for Chinese characters in Taiwan when it was under Japanese rule.

Kanji (/ˈkændʒi, ˈkɑːn-/; Japanese: 漢字, pronounced [kaɲ.dʑi] ,'Chinese characters') are logographic Chinese characters, adapted from Chinese script, used in the writing of Japanese. They comprised a major part of the Japanese writing system during the time of Old Japanese and are still used, along with the subsequently derived syllabic scripts of hiragana and katakana. The characters have Japanese pronunciations; most have two, with one based on the Chinese sound. A few characters were invented in Japan by constructing character components derived from other Chinese characters. After the Meiji Restoration, Japan made its own efforts to simplify the characters, now known as shinjitai, by a process similar to China's simplification efforts, with the intention to increase literacy among the general public. Since the 1920s, the Japanese government has published character lists periodically to help direct the education of its citizenry through the myriad Chinese characters that exist. There are nearly 3,000 kanji used in Japanese names and in common communication.

The term kanji in Japanese literally means "Han characters". Japanese kanji and Chinese hanzi (traditional Chinese: 漢字; simplified Chinese: 汉字; pinyin: hànzì; lit. 'Han characters') share a common foundation. The significant use of Chinese characters in Japan first began to take hold around the 5th century AD and has since had a profound influence in shaping Japanese culture, language, literature, history, and records. Inkstone artifacts at archaeological sites dating back to the earlier Yayoi period were also found to contain Chinese characters.

Hiragana (平仮名, ひらがな; IPA: [çiɾaɡaꜜna, çiɾaɡana(ꜜ)]) is a Japanese syllabary, part of the Japanese writing system, along with katakana as well as kanji (Chinese characters).

It is a phonetic lettering system. The word hiragana means "common" or "plain" kana (originally also "easy", as contrasted with kanji).

In modern Japanese, ateji (当て字, 宛字 or あてじ; pronounced [ate(d)ʑi]; "assigned characters") principally refers to kanji used to phonetically represent native or borrowed words with less regard to the underlying meaning of the characters. This is similar to man'yōgana in Old Japanese. Conversely, ateji also refers to kanji used semantically without regard to the readings.

For example, the word "sushi" is often written with its ateji "寿司". Though the two characters have the readings 'su' and 'shi' respectively, the character '寿' means "one's natural life span" and '司' means "to administer", neither of which has anything to do with the food. Ateji as a means of representing loanwords has been largely superseded in modern Japanese by the use of katakana, although many ateji coined in earlier eras still linger on.

In the Japanese language, the gojūon (五十音; Japanese pronunciation: [ɡo(d)ʑɯꜜːoɴ], lit. 'fifty sounds') is a traditional system ordering kana characters by their component phonemes, roughly analogous to alphabetical order. The "fifty" (gojū) in its name refers to the 5×10 grid in which the characters are displayed. Each kana, which may be a hiragana or katakana character, corresponds to one sound in Japanese. As depicted at the right using hiragana characters, the sequence begins with あ (a), い (i), う (u), え (e), お (o), then continues with か (ka), き (ki), く (ku), け (ke), こ (ko), and so on and so forth for a total of ten rows of five columns.

Although nominally containing 50 characters, the grid is not completely filled, and, further, there is an extra character added outside the grid at the end: with 5 gaps and 1 extra character, the current number of distinct kana in a moraic chart in modern Japanese is therefore 46. Some of these gaps have always existed as gaps in sound: there was no yi or wu even in Old Japanese, with the kana for i and u doubling up for those phantom values. Ye persisted long enough for kana to be developed for it, but disappeared in Early Middle Japanese, having merged with e. Much later, with the spelling reforms after World War II, the kana for wi and we were replaced with i and e, the sounds they had merged with. The kana for moraic n (hiragana ん) is not part of the grid, as it was introduced long after the gojūon ordering was devised. (Previously mu (hiragana む) was used for this sound.)

Gairaigo (外来語; Japanese pronunciation: [ɡaiɾaiɡo]) is Japanese for "loan word", and indicates a transcription into Japanese. In particular, the word usually refers to a Japanese word of foreign origin that was not borrowed in ancient times from Old or Middle Chinese (especially Literary Chinese), but in modern times, primarily from English, Portuguese, Dutch, and modern Chinese languages, such as Standard Chinese and Cantonese. These are primarily written in the katakana phonetic script, with a few older terms written in Chinese characters (kanji); the latter are known as ateji.

Japanese has many loan words from Chinese, accounting for a sizeable fraction of the language. These words were borrowed during ancient times and are written in kanji. Modern Chinese loanwords are generally considered gairaigo and written in katakana, or sometimes written in kanji (either with the more familiar word as a base text gloss and the intended katakana as furigana or vice versa); pronunciation of modern Chinese loanwords generally differs from the corresponding usual pronunciation of the characters in Japanese.