Romaji

The romanization of Japanese is the application of the Latin script to write the Japanese language. This method of writing is sometimes referred to in English as rōmaji (ローマ字^?, literally, "roman letters") (Japanese pronunciation: [ɽóːmadʑi]  listen ), sometimes incorrectly transliterated with an n as rōmanji. There are several different romanization systems. The three main ones are Hepburn romanization, Kunrei-shiki romanization (ISO 3602), and Nihon-shiki romanization (ISO 3602 Strict). Variants of the Hepburn system are the most widely used.

Japanese is normally written in a combination of logographic characters borrowed from Chinese (kanji) and syllabic scripts (kana) which also ultimately derive from Chinese characters. Rōmaji may be used in any context where Japanese text is targeted at non-Japanese speakers who cannot read kanji or kana, such as for names on street signs and passports, and in dictionaries and textbooks for foreign learners of the language. It is also used to transliterate Japanese terms in text written in English (or other languages that use the Latin script) on topics related to Japan, such as linguistics, literature, history, and culture. Rōmaji is the most common way to input Japanese into word processors and computers, and may also be used to display Japanese on devices that do not support the display of Japanese characters.

...
Wikipedia