English Reference
noun · adjective

legion

n. · adj.
US /ˈɫidʒən/ UK /lˈiːdʒən/ le·gion UK spelling legion's, legion's

  1. 01 B2 Upper Intermediate Law

    n.a large group of soldiers in the army of Ancient Rome.

    n.the principal unit of the Roman army, typically consisting of 3,000 to 6,000 infantry and a small cavalry component.

    Simple

    The Roman legion marched across the bridge to reach the city.

    In context

    Historians estimate that a single Roman legion at full strength could maintain control over a vast territory through disciplined engineering and logistics.

  2. 02 C1 Advanced Literary

    n.a very large number of people or things.

    n.a vast multitude or a great number of people or things.

    Simple

    A legion of fans waited outside the stadium to see the singer.

    In context

    The author faced a legion of critics who disagreed with his interpretation of the historical data.

  3. 03 B2 Upper Intermediate

    n.a national organization for people who used to be in the military.

    n.a national association of former military personnel, often involved in advocacy and social support.

    Simple

    My grandfather goes to the local legion every Friday to meet his old friends.

    In context

    The Royal British Legion provides essential financial and emotional support to veterans and their families across the United Kingdom.

  4. 04 C1 Advanced Formal

    adj.used to say that there are a very great number of something.

    adj.existing in great numbers; numerous or vast.

    Simple

    The problems with the new software are legion.

    In context

    While the benefits of the new policy are clear, the potential administrative hurdles are legion and require careful planning.

    Usage

    Always used after the noun it describes, following the verb 'to be'.

It became a cult classic, inspiring a legion of copycats.

The Guardian· 3 Sept 2026

Our thoughts and prayers are with her family, her legion of fans, and everyone who loved her.

The Guardian· 26 Aug 2026

Attested (in Middle English, as legioun) around 1200, from Old French legion, from Latin legiō, legionem, from legō (“to gather, collect”); akin to legend, lecture. Doublet of León, which was borrowed from Spanish. Generalized sense of “a large number” is due to an allusive phrase in Mark 5:9, "My name is Legion, for we are many".

Etymology adapted from Wiktionary, available under CC BY-SA 4.0.

This entry
Origin Latin legiō
Level C1 · Advanced
Frequency Frequent
Updated