1.
Roman letters, romaji, the Latin alphabet
The Latin alphabet (A-Z) used to write Japanese phonetically. Also refers to the romanization system itself.
ローマ字 literally means "Roman characters" and refers to the Latin alphabet as used to represent Japanese.
Common collocations
Romanization systems
There are several romanization systems, including 訓令式 (Kunrei-shiki, taught in Japanese schools) and ヘボン式 (Hepburn, used on passports and signs). Hepburn is the most widely recognized internationally.
Usage
Most Japanese people type using ローマ字入力, where they type romanized letters that are automatically converted to kana.
Related Words
Related:
漢字 (Chinese characters)
Related:
平仮名 (hiragana)
Related:
片仮名 (katakana)
Compare:
英字 (Roman letters)