A macron, from Greek (makrón) meaning "long",'s a diacritic placed over or under a vowel, originally used to mark a long (for example, heavy) syllable in Græco-Roman metrics, but now also indicates that the vowel's long. (The opposite's a breve ˘, used to indicate originally a short syllable and now also a short vowel.) Distinctions between long and short vowels are usually phonemic. In the International Phonetic Alphabet the macron's used to indicate mid tone; the sign for a lon… (More on Macron)