umlaut
noun [ C ] uk/ˈʊm.laʊt/ us/ˈʊm.laʊt/
（德语等语言中表示元音发音发生变化的）变音符
a mark put over a vowel in some languages, such as German, to show that the pronunciation of the vowel is changed
The German word "Gebäude", which means "building", has an umlaut over the "a". 德语词 Gebäude 意思是“建筑物”，其元音 a 字母上有一个变音符。