IPA: /ˈmækrɒn/
KK: /ˈmæk.rɒn/
A symbol placed above a vowel to show that the vowel is pronounced for a longer duration or has a specific phonetic value.
In the word 'fāther', the macron over the 'a' indicates that it is a long vowel sound.
Macron comes from the Greek word "makron" (meaning long). In linguistic terms, it refers to a diacritical mark placed over a vowel to indicate that it is to be pronounced with a long sound. Thus, a macron signifies a longer vowel sound in pronunciation.
Think of the Greek word for long ('makron') to remember that a macron indicates a longer vowel sound.