| Definition -
A straight horizontal line placed over a vowel to indicate that it is long.
1. Its opposite is the breve, which is used to show that the vowel is short.
Etymology - The term derives from the Greek macros, long.
Oxford English Dictionary - Its first citation is from 1851:
"The different uses made of the breve, the macron, and the accents."
(G. Brown Gram. of Gramm. 810 note)