A macron is a diacritic ¯ placed over a vowel. It is usually used in pronunciation guides as an indication that the vowel has a long sound. In Hawaiian it is used to indicate long vowels, which in turn influence the placement of accent stress in words. In Latvian it is used to indicate a long A sound. The macron is also used in the Hepburn transcription of Japanese to indicate a long vowel, as in kōtsū (交通) 'traffic' as opposed to kotsu (骨) 'bone' or 'knack (fig.)'. In Pinyin it is used to indicate one of four Mandarin tones. It is often used in modern Latin dictionaries to mark vowel length.
Vowel length in New Zealand Māori is phonemic, i.e. vowels are either pronounced short or long. Early writing in Māori did not distinguish vowel length. Some have advocated that the double vowel orthography be used to distinguish vowel length. However, the Māori Language Commission (Te Taura Whiri) advocate a macron be used to designate a long vowel. The use of the macron is now wide spread in modern Māori writings, though many people use a diaeresis mark instead (e.g. Mäori instead of Māori) due to lack of support on computers.
In Unicode, "combining macron" is one of the combining diacritical marks, its code is U+0304 (in HTML, ̄ or ̄). There are also several precomposed characters; their HTML/Unicode numbers are:
| Upper Case | Lower Case | ||
| Character | HTML Code | Character | HTML Code |
| Ā | Ā | ā | ā |
| Ē | Ē | ē | ē |
| Ī | Ī | ī | ī |
| Ō | Ō | ō | ō |
| Ū | Ū | ū | ū |
| Ǖ | Ǖ | ǖ | ǖ |
The final row is the letter U/u with macron and diaeresis, used in pinyin to indicate the letter ü pronounced with the first tone.