Vowel length is indicated by a macron ("ā") or a breve ("ă") for long and short vowels, respectively. Open vowels are marked by a line under the letter ("e̱"), while a dot below the letter makes it a close vowel ("ẹ"). Rounded front vowels are written with an umlaut ("ö" and "ü" ), either on top or below, when the space above the letter is needed for vowel length marks (thus "ṳ̄" or "ṳ̆"). Unrounded back vowels are indicated by a 'hook' (ogonek) on "ę" or "į". Central vowels may be written as one of these series, or as reduced vowels.