Kanji or literally Han characters in Japan. 2,136 regular characters.
Romaji can be used by Westerners to type the Latin script.
Hiragana is a phonetic lettering system with 46 base sounds. Started in the 5th Century.
Katakana is another Japanese script with 46 base sounds. Used for loan words and emphasis. Started by monks in the 9th Century.
Mainly the text is written with hiragana and kanji in current Japanese language. Katakana is used when they write a word or name from non Chinese countries and when they are designated to write katakana. And when they don't know kanji, they write hiragana or katakana instead of kanji.
Click here to convert between Romaji, Hiragana, Katakana and possible Kanji
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