Nihon-shiki, or Nippon-shiki Rōmaji (Japanese: 日本式ローマ字, "Japan-style," romanized as Nihon-siki or Nippon-siki in Nippon-shiki itself), is a romanization system for transliterating the Japanese language into the Latin alphabet. In discussion about romaji, it is abbreviated as Nihon-shiki or Nippon-shiki. Among the major romanization systems for Japanese, it is the most regular one and has a one-to-one relation to the kana writing system.
It was invented by physicist Aikitsu Tanakadate (田中館 愛橘) in 1885, with the intention to replace the Hepburn system of romanization. Tanakadate's intention was to replace the traditional kanji and kana system of writing Japanese completely by a romanized system, which he felt would make it easier for Japan to compete with Western countries. Since the system was intended for Japanese people to use to write their own language, it is much more regular than Hepburn romanization, and unlike Hepburn's system, it makes no effort to make itself easier to pronounce for English speakers.
Nippon-shiki was followed by Kunrei-shiki, which was adopted in 1937, after a political debate over whether Nihon-shiki or Hepburn-shiki should be used by the Japanese government. Kunrei is otherwise nearly identical, but it merges syllable pairs di/zi ぢ/じ, du/zu づ/ず, dya/zya ぢゃ/じゃ, dyu/zyu ぢゅ/じゅ, dyo/zyo ぢょ/じょ, wi/i ゐ/い, we/e ゑ/え, kwa/ka くゎ/か, and gwa/ga ぐゎ/が; their pronunciations in modern standard Japanese have become identical. For example, the word かなづかい, rendered kanadukai in Nippon-shiki, is pronounced as kanazukai in modern Japanese, and is romanized as such in Kunrei.
Nippon-shiki is considered the most regular of the romanization systems for the Japanese language because it maintains a strict "one kana, two letters" form. Because it has unique forms corresponding to each of the respective pairs of kana homophones listed above, it is the only formal system of romanization that can allow (almost) lossless ("round trip") mapping, but the standard does not mandate the precise spellings needed to distinguish ô 王/おう, ou 追う/おう and oo 大/おお. (See the hiragana article for more details.)
Nippon-shiki has been established by the International Organization for Standardization in the ISO 3602 strict form. The JSL system, which is intended for use instructing foreign students of Japanese, is also based on Nippon-shiki.
|あ/ア a||い/イ i||う/ウ u||え/エ e||お/オ o||(ya)||(yu)||(yo)|
|か/カ ka||き/キ ki||く/ク ku||け/ケ ke||こ/コ ko||きゃ/キャ kya||きゅ/キュ kyu||きょ/キョ kyo|
|さ/サ sa||し/シ si||す/ス su||せ/セ se||そ/ソ so||しゃ/シャ sya||しゅ/シュ syu||しょ/ショ syo|
|た/タ ta||ち/チ ti||つ/ツ tu||て/テ te||と/ト to||ちゃ/チャ tya||ちゅ/チュ tyu||ちょ/チョ tyo|
|な/ナ na||に/ニ ni||ぬ/ヌ nu||ね/ネ ne||の/ノ no||にゃ/ニャ nya||にゅ/ニュ nyu||にょ/ニョ nyo|
|は/ハ ha||ひ/ヒ hi||ふ/フ hu||へ/ヘ he||ほ/ホ ho||ひゃ/ヒャ hya||ひゅ/ヒュ hyu||ひょ/ヒョ hyo|
|ま/マ ma||み/ミ mi||む/ム mu||め/メ me||も/モ mo||みゃ/ミャ mya||みゅ/ミュ myu||みょ/ミョ myo|
|や/ヤ ya||ゆ/ユ yu||よ/ヨ yo|
|ら/ラ ra||り/リ ri||る/ル ru||れ/レ re||ろ/ロ ro||りゃ/リャ rya||りゅ/リュ ryu||りょ/リョ ryo|
|わ/ワ wa||ゐ/ヰ wi||ゑ/ヱ we||を/ヲ wo|
|voiced sounds (dakuten)|
|が/ガ ga||ぎ/ギ gi||ぐ/グ gu||げ/ゲ ge||ご/ゴ go||ぎゃ/ギャ gya||ぎゅ/ギュ gyu||ぎょ/ギョ gyo|
|ざ/ザ za||じ/ジ zi||ず/ズ zu||ぜ/ゼ ze||ぞ/ゾ zo||じゃ/ジャ zya||じゅ/ジュ zyu||じょ/ジョ zyo|
|だ/ダ da||ぢ/ヂ di||づ/ヅ du||で/デ de||ど/ド do||ぢゃ/ヂャ dya||ぢゅ/ヂュ dyu||ぢょ/ヂョ dyo|
|ば/バ ba||び/ビ bi||ぶ/ブ bu||べ/ベ be||ぼ/ボ bo||びゃ/ビャ bya||びゅ/ビュ byu||びょ/ビョ byo|
|ぱ/パ pa||ぴ/ピ pi||ぷ/プ pu||ぺ/ペ pe||ぽ/ポ po||ぴゃ/ピャ pya||ぴゅ/ピュ pyu||ぴょ/ピョ pyo|