macron       
noun [ C ]  phonetics, language specialized uk/ˈmæk.rɒn/ us/ˈmeɪ.krɑːn/ /ˈmæk.rɑːn/
 长音符号(ˉ)
a symbol (ˉ) written or printed above a vowel to show that it is pronounced with a long sound
  "Maori" should be written with a macron on the "a". “Maori”应该在“a”上加一个长音符号。 
 The five vowels come in long and short forms; the long form is sometimes signified in print by a macron (a flat bar) above the letter. 五个元音的发音有长短之分,在书面上有时会在长元音上加长音符号(一条短横线)来进行标注。 
 Compare: breve (PRONUNCIATION) 
 - More examples
 - Macrons have been omitted in well-known place names such as Tokyo and Kyoto.
 - The user must contend with macrons over some vowels.
 - Long vowels are indicated by placing a line or bar above the vowel. This is a diacritical mark known as a macron.