A macron is a small horizontal line placed over a vowel to show that it should be pronounced with a long sound. In Latin and Ancient Greek, the macron tells you to hold the vowel longer, like the difference between a quick “a” in “cat” and the stretched-out “a” in “father.”

You might see macrons in dictionaries showing how to pronounce words from other languages. In Japanese written with Roman letters (called romaji), a macron over an “o” (ō) means you hold that “oh” sound longer, like in Tōkyō. In Hawaiian, macrons (called kahakō) can change meanings entirely: kau means “to place,” but kāu means “yours.”

The macron helps readers know exactly how a word should sound, especially in languages where vowel length matters. Without it, you might mispronounce a foreign word or miss an important distinction. Think of it as a musical note telling you to hold a sound longer than usual.