EDIT Languages: Latvian, Lithuanian

History and examples of use
Macron above a character lengthtens the vowels ā, ē, ī, ō, and ū in Latvian, ū in Lithuanian. It denotes stress in Latin and also while latinising non-Latin alphabets. In some Arabic transliterations, the ā and the ū are used to represents the sound "a" as in "cat" and "oo" as in "soon" respectively.

Notes
The government of Soviet Lithuania got rid of the ō/Ō character in written Lithuanian, and in Lithuania, this rule is abided to since. However, in the Lithuanian communities abroad, the original orthography is used. In old German typography the macron was used instead of doubling the character: ē = ee.
Macron also denotes one of the five tones in the pinyin romanised version of Mandarin Chinese.

Type Design
The stroke thickness should be the same as the thickness of vertical strokes in the typeface (such as in H), the width may be the same as caron or circumflex width. Because of the variable width of the characters that may need macron with them, variable width of macron is preferable — narrower for i, wider for æ.

From: diacritics.typo.cz

25th of May 2005

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