<Tr> <Td> Ӹ </Td> <Td> ӹ </Td> </Tr> <Tr> <Td> Ӭ </Td> <Td> ӭ </Td> </Tr> <P> The diaeresis (UK: / daɪˈɪrɪsɪs /, US: / daɪˈɛrɪsɪs / dy - ERR - i - sis; plural: diaereses), also spelled diæresis or dieresis and also known as the tréma (also: trema) or the umlaut, is a diacritical mark that consists of two dots (_̈) placed over a letter, usually a vowel . When that letter is an i or a j, the diacritic replaces the tittle: ï . </P> <P> The diaeresis and the umlaut are diacritics marking two distinct phonological phenomena . The diaeresis represents the phenomenon also known as diaeresis or hiatus in which a vowel letter is not pronounced as part of a digraph or diphthong . The umlaut (/ ˈʊmlaʊt / UUM - lowt), in contrast, indicates a sound shift . These two diacritics originated separately; the diaeresis is considerably older . Nevertheless, in modern computer systems using Unicode, the umlaut and diaeresis diacritics are identical, e.g. U + 00E4 ä LATIN SMALL LETTER A WITH DIAERESIS (HTML & #228; &auml;) represents both a-umlaut and a-diaeresis . </P>

What is the name of the two dots over a vowel