1. The major unit of the Roman army consisting of 3,000 to 6,000 infantry troops and 100 to 200 cavalry troops.
2. A large military unit trained for combat; an army.
3. A large number; a multitude. See Synonyms at multitude.
4. often Legion A national organization of former members of the armed forces.
Constituting a large number; multitudinous: Her admirers were legion. His mistakes were legion.
[Middle English legioun, from Old French legion, from Latin legiō, legiōn-, from legere, to gather; see leg- in the Appendix of Indo-European roots.]
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2018 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
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.