Overview

The complete katakana script consists of 48 characters, not counting functional and diacritic marks:

• 5 nucleus vowels
• 42 core or body (onset-nucleus) syllabograms, consisting of nine consonants in combination with each of the five vowels, of which three possible combinations (yi, ye, wu) are not canonical
• 1 coda consonant

These are conceived as a 5×10 grid (gojūon, 五十音, literally "fifty sounds"), as shown in the adjacent table, read ア (a), イ (i), ウ (u), エ (e), オ (o), カ (ka), キ (ki), ク (ku), ケ (ke), コ (ko) and so on. The gojūon inherits its vowel and consonant order from Sanskrit practice. In vertical text contexts, which used to be the default case, the grid is usually presented as 10 columns by 5 rows, with vowels on the right hand side and ア (a) on top. Katakana glyphs in the same row or column do not share common graphic characteristics. Three of the syllabograms to be expected, yi, ye and wu, may have been used idiosyncratically with varying glyphs, but never became conventional in any language and are not present at all in modern Japanese.

The 50-sound table is often amended with an extra character, the nasal ン (n). This can appear in several positions, most often next to the N signs or, because it developed from one of many mu hentaigana, below the u column. It may also be appended to the vowel row or the a column. Here, it is shown in a table of its own.

The script includes two diacritic marks placed at the upper right of the base character that change the initial sound of a syllabogram. A double dot, called dakuten, indicates a primary alteration; most often it voices the consonant: k→g, s→z, t→d and h→b; for example, カ (ka) becomes ガ (ga). Secondary alteration, where possible, is shown by a circular handakuten: h→p; For example; ハ (ha) becomes パ (pa). Diacritics, though used for over a thousand years, only became mandatory in the Japanese writing system in the second half of the 20th century. Their application is strictly limited in proper writing systems, but may be more extensive in academic transcriptions.

Furthermore, some characters may have special semantics when used in smaller sizes after a normal one (see below), but this does not make the script truly bicameral.

The layout of the gojūon table promotes a systematic view of kana syllabograms as being always pronounced with the same single consonant followed by a vowel, but this is not exactly the case (and never has been). Existing schemes for the romanization of Japanese either are based on the systematic nature of the script, e.g. nihon-shiki チ ti, or they apply some Western graphotactics, usually the English one, to the common Japanese pronunciation of the kana signs, e.g. Hepburn-shiki チ chi. Both approaches conceal the fact, though, that many consonant-based katakana signs, especially those canonically ending in u, can be used in coda position, too, where the vowel is unvoiced and therefore barely perceptible.

Japanese

Usage

Main article: Japanese writing system

Collection of poems by priest Myōe, 1248

In modern Japanese, katakana is most often used for transcription of words from foreign languages or loanwords (other than words historically imported from Chinese), called gairaigo.^[5] For example, "ice cream" is written アイスクリーム (aisukurīmu). Similarly, katakana is usually used for country names, foreign places, and foreign personal names. For example, the United States is usually referred to as アメリカ (Amerika), rather than in its ateji kanji spelling of 亜米利加 (Amerika).

Katakana are also used for onomatopoeia,^[5] words used to represent sounds – for example, ピンポン (pinpon), the "ding-dong" sound of a doorbell.

Technical and scientific terms, such as the names of animal and plant species and minerals, are also commonly written in katakana.^[6] Homo sapiens, as a species, is written ヒト (hito), rather than its kanji 人.

Katakana are often (but not always) used for transcription of Japanese company names. For example, Suzuki is written スズキ, and Toyota is written トヨタ. As these are common family names, Suzuki being the second most common in Japan,^[7] using katakana helps distinguish company names from surnames in writing. Katakana are commonly used on signs, advertisements, and hoardings (i.e., billboards), for example, ココ (koko, "here"), ゴミ (gomi, "trash"), or メガネ (megane, "glasses"). Words the writer wishes to emphasize in a sentence are also sometimes written in katakana, mirroring the usage of italics in European languages.^[5]

Pre–World War II official documents mix katakana and kanji in the same way that hiragana and kanji are mixed in modern Japanese texts, that is, katakana were used for okurigana and particles such as wa or o.

Katakana was also used for telegrams in Japan before 1988, and for computer systems – before the introduction of multibyte characters – in the 1980s. Most computers of that era used katakana instead of kanji or hiragana for output.

Although words borrowed from ancient Chinese are usually written in kanji, loanwords from modern Chinese dialects that are borrowed directly use katakana instead.

Examples of modern Chinese loanwords in Japanese

Japanese	Hepburn	Meaning	Chinese	Pinyin/Yale	Source language
マージャン	mājan	mahjong	麻將	májiàng	Mandarin
ウーロン茶	ūroncha	Oolong tea	烏龍茶	wūlóngchá
チャーハン	chāhan	fried rice	炒飯	chǎofàn
チャーシュー	chāshū	barbecued pork	叉燒	chā sīu	Cantonese
シューマイ	shūmai	shumai	燒賣	sīu máai

The very common Chinese loanword rāmen, written in katakana as ラーメン, is rarely written with its kanji (拉麺).

There are rare instances where the opposite has occurred, with kanji forms created from words originally written in katakana. An example of this is コーヒー kōhī, ("coffee"), which can alternatively be written as 珈琲. This kanji usage is occasionally employed by coffee manufacturers or coffee shops for novelty.

Katakana is used to indicate the on'yomi (Chinese-derived readings) of a kanji in a kanji dictionary. For instance, the kanji 人 has a Japanese pronunciation, written in hiragana as ひと hito (person), as well as a Chinese derived pronunciation, written in katakana as ジン jin (used to denote groups of people). Katakana is sometimes used instead of hiragana as furigana to give the pronunciation of a word written in Roman characters, or for a foreign word, which is written as kanji for the meaning, but intended to be pronounced as the original.

In this travel warning, the kanji for "fog" (霧) has been written in katakana (キリ) to make it more immediately readable.

Katakana are also sometimes used to indicate words being spoken in a foreign or otherwise unusual accent. For example, in a manga, the speech of a foreign character or a robot may be represented by コンニチワ konnichiwa ("hello") instead of the more typical hiragana こんにちは. Some Japanese personal names are written in katakana. This was more common in the past, hence elderly women often have katakana names. This was particularly common among women in the Meiji and Taishō periods, when many poor, illiterate parents were unwilling to pay a scholar to give their daughters names in kanji.^[8] Katakana is also used to denote the fact that a character is speaking a foreign language, and what is displayed in katakana is only the Japanese "translation" of their words.

Some frequently used words may also be written in katakana in dialogs to convey an informal, conversational tone. Some examples include マンガ ("manga"), アイツ aitsu ("that guy or girl; he/him; she/her"), バカ baka ("fool"), etc.

Words with difficult-to-read kanji are sometimes written in katakana (hiragana is also used for this purpose). This phenomenon is often seen with medical terminology. For example, in the word 皮膚科 hifuka ("dermatology"), the second kanji, 膚, is considered difficult to read, and thus the word hifuka is commonly written 皮フ科 or ヒフ科, mixing kanji and katakana. Similarly, difficult-to-read kanji such as 癌 gan ("cancer") are often written in katakana or hiragana.

Katakana is also used for traditional musical notations, as in the Tozan-ryū of shakuhachi, and in sankyoku ensembles with koto, shamisen and shakuhachi.

Some instructors teaching Japanese as a foreign language "introduce katakana after the students have learned to read and write sentences in hiragana without difficulty and know the rules."^[9] Most students who have learned hiragana "do not have great difficulty in memorizing" katakana as well.^[10] Other instructors introduce katakana first, because these are used with loanwords. This gives students a chance to practice reading and writing kana with meaningful words. This was the approach taken by the influential American linguistics scholar Eleanor Harz Jorden in Japanese: The Written Language (parallel to Japanese: The Spoken Language).^[11]

A page of the Meiji Constitution written exclusively with kyūjitai and katakana

Ainu

Katakana is commonly used by Japanese linguists to write the Ainu language. In Ainu katakana usage, the consonant that comes at the end of a syllable is represented by a small version of a katakana that corresponds to that final consonant followed by a vowel (for details of which vowel, please see the table at Ainu language § Special katakana for the Ainu language). For instance, the Ainu word up is represented by ウㇷ゚ (ウプ [u followed by small pu]). Ainu also uses three handakuten modified katakana: セ゚ ([tse]) and either ツ゚ or ト゚ ([tu̜]). In Unicode, the Katakana Phonetic Extensions block (U+31F0–U+31FF) exists for Ainu language support. These characters are used for the Ainu language only.

Taiwanese

Taiwanese kana (タイ ヲァヌ ギイ カア ビェン) is a katakana-based writing system once used to write Holo Taiwanese, when Taiwan was under Japanese control. It functioned as a phonetic guide for Chinese characters, much like furigana in Japanese or Zhùyīn fúhào in Chinese. There were similar systems for other languages in Taiwan as well, including Hakka and Formosan languages.

Unlike Japanese or Ainu, Taiwanese kana are used similarly to the zhùyīn fúhào characters, with kana serving as initials, vowel medials and consonant finals, marked with tonal marks. A dot below the initial kana represents aspirated consonants, and チ, ツ, サ, セ, ソ, ウ and オ with a superpositional bar represent sounds found only in Taiwanese.

Okinawan

Katakana is used as a phonetic guide for the Okinawan language, unlike the various other systems to represent Okinawan, which use hiragana with extensions. The system was devised by the Okinawa Center of Language Study of the University of the Ryukyus. It uses many extensions and yōon to show the many non-Japanese sounds of Okinawan.

Extended katakana

Using small versions of the five vowel kana, many digraphs have been devised, mainly to represent the sounds in words of other languages.

Digraphs with orange backgrounds are the general ones used for loanwords or foreign places or names, and those with blue backgrounds are used for more accurate transliterations of foreign sounds, both suggested by the Cabinet of Japan's Ministry of Education, Culture, Sports, Science and Technology.^[12] Katakana combinations with beige backgrounds are suggested by the American National Standards Institute^[13] and the British Standards Institution as possible uses.^[14] Ones with purple backgrounds appear on the 1974 version of the Hyōjun-shiki formatting.^[15]

Pronunciations are shown in Hepburn romanization.

• * — The use of ウ in these two cases to represent w is rare in modern Japanese except for Internet slang and transcription of the Latin sound [w] into katakana. E.g.: ミネルウァ (Mineruwa "Minerva", from Latin MINERVA [mɪˈnɛrwa]); ウゥルカーヌス (Wurukānusu "Vulcan", from Latin VVLCANVS, Vulcānus [wʊlˈkaːnʊs]). The wa-type of foreign sounds (as in watt or white) is usually transcribed to ワ (wa), while the wu-type (as in wood or woman) is usually to ウ (u) or ウー (ū).
• ii — ヴ has a rarely-used hiragana form in ゔ that is also vu in Hepburn romanization systems.
• iii — The characters in green are obsolete in modern Japanese and very rarely used.^[16][17]
• * * – ヌィ is the same as ニ but with an alveolar n, despite never having been used

Variant forms

Katakana have variant forms. For example, (ネ) and (ヰ).^[21] However, katakana's variant forms are fewer than hiragana's ones. Katakana's choices of man'yōgana segments had stabilized early on and established – with few exceptions – an unambiguous phonemic orthography (one symbol per sound) long before the 1900 script regularization.^[22]

Polysyllabic kana

Yi, Ye and Wu

Hiragana and katakana

In addition to the usual full-width (全角, zenkaku) display forms of characters, katakana has a second form, half-width (半角, hankaku) (there are no kanji). The half-width forms were originally associated with the JIS X 0201 encoding. Although their display form is not specified in the standard, in practice they were designed to fit into the same rectangle of pixels as Roman letters to enable easy implementation on the computer equipment of the day. This space is narrower than the square space traditionally occupied by Japanese characters, hence the name "half-width". In this scheme, diacritics (dakuten and handakuten) are separate characters. When originally devised, the half-width katakana were represented by a single byte each, as in JIS X 0201, again in line with the capabilities of contemporary computer technology.

In the late 1970s, two-byte character sets such as JIS X 0208 were introduced to support the full range of Japanese characters, including katakana, hiragana and kanji. Their display forms were designed to fit into an approximately square array of pixels, hence the name "full-width". For backward compatibility, separate support for half-width katakana has continued to be available in modern multi-byte encoding schemes such as Unicode, by having two separate blocks of characters – one displayed as usual (full-width) katakana, the other displayed as half-width katakana.

Although often said to be obsolete, the half-width katakana are still used in many systems and encodings. For example, the titles of mini discs can only be entered in ASCII or half-width katakana, and half-width katakana are commonly used in computerized cash register displays, on shop receipts, and Japanese digital television and DVD subtitles. Several popular Japanese encodings such as EUC-JP, Unicode and Shift JIS have half-width katakana code as well as full-width. By contrast, ISO-2022-JP has no half-width katakana, and is mainly used over SMTP and NNTP.

Unicode

Katakana was added to the Unicode Standard in October, 1991 with the release of version 1.0.

The Unicode block for (full-width) katakana is U+30A0–U+30FF.

Encoded in this block along with the katakana are the nakaguro word-separation middle dot, the chōon vowel extender, the katakana iteration marks, and a ligature of コト sometimes used in vertical writing.

Half-width equivalents to the usual full-width katakana also exist in Unicode. These are encoded within the Halfwidth and Fullwidth Forms block (U+FF00–U+FFEF) (which also includes full-width forms of Latin characters, for instance), starting at U+FF65 and ending at U+FF9F (characters U+FF61–U+FF64 are half-width punctuation marks). This block also includes the half-width dakuten and handakuten. The full-width versions of these characters are found in the Hiragana block.

Circled katakana are code points U+32D0–U+32FE in the Enclosed CJK Letters and Months block (U+3200–U+32FF). A circled ン (n) is not included.

Extensions to Katakana for phonetic transcription of Ainu and other languages were added to the Unicode standard in March 2002 with the release of version 3.2.

The Unicode block for Katakana Phonetic Extensions is U+31F0–U+31FF:

Historic and variant forms of Japanese kana characters were added to the Unicode standard in October 2010 with the release of version 6.0.

The Unicode block for Kana Supplement is U+1B000–U+1B0FF:

The Unicode block for Small Kana Extension is U+1B130–U+1B16F:

The Kana Extended-A Unicode block is U+1B100–1B12F. It contains hentaigana (non-standard hiragana) and historic kana characters.

The Kana Extended-B Unicode block is U+1AFF0–1AFFF. It contains kana originally created by Japanese linguists to write Taiwanese Hokkien known as Taiwanese kana.

Katakana in other Unicode blocks:

• Dakuten and handakuten diacritics are located in the Hiragana block:
  • U+3099 COMBINING KATAKANA-HIRAGANA VOICED SOUND MARK (non-spacing dakuten): ゙
  • U+309A COMBINING KATAKANA-HIRAGANA SEMI-VOICED SOUND MARK (non-spacing handakuten): ゚
  • U+309B KATAKANA-HIRAGANA VOICED SOUND MARK (spacing dakuten): ゛
  • U+309C KATAKANA-HIRAGANA SEMI-VOICED SOUND MARK (spacing handakuten): ゜
• Two katakana-based emoji are in the Enclosed Ideographic Supplement block:
  • U+1F201 SQUARED KATAKANA KOKO ('here' sign): 🈁
  • U+1F202 SQUARED KATAKANA SA ('service' sign): 🈂
• A katakana-based Japanese TV symbol from the ARIB STD-B24 standard is in the Enclosed Ideographic Supplement block:
  • U+1F213 SQUARED KATAKANA DE ('data broadcasting service linked with a main program' symbol): 🈓

Furthermore, as of Unicode 15.1, the following combinatory sequences have been explicitly named, despite having no precomposed symbols in the katakana block. Font designers may want to optimize the display of these composed glyphs. Some of them are mostly used for writing the Ainu language, the others are called bidakuon in Japanese. Other, arbitrary combinations with U+309A handakuten are also possible.