ma·cron (mākrŏn′, -krən, măkrŏn′)
1. A symbol ( ¯ ) placed over a vowel to show that it has a long sound.
2. The horizontal mark ( ¯ ) used to indicate a stressed or long syllable in a foot of verse.
[Greek makron, from neuter of makros, long; see māk- in the Appendix of Indo-European roots.]
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Indo-European & Semitic Roots Appendices
Thousands of entries in the dictionary include etymologies that trace their origins back to reconstructed proto-languages. You can obtain more information about these forms in our online appendices:
The Indo-European appendix covers nearly half of the Indo-European roots that have left their mark on English words. A more complete treatment of Indo-European roots and the English words derived from them is available in our Dictionary of Indo-European Roots.