long-vowel mark

In katakana, a long vowel is indicated by a long dash-like mark called 長音符 (chōonpu). It extends the preceding vowel sound.

In hiragana, a long vowel is written by adding the corresponding vowel kana: あ for a, い for i/e, う for u/o. For e, い is usually used, but sometimes え; for o, う is usually used, but sometimes お.

In romaji, long vowels are often indicated by a macron (e.g., ā) or by doubling the vowel (e.g., aa). The macron is standard in Hepburn romanization, while doubling is used in some systems or when macrons are unavailable.