English Reference
noun

realm

n.
US /ˈɹɛɫm/ UK /ɹˈɛlm/ realm UK spelling realm's, realm's

  1. 01 B2 Upper Intermediate

    a specific area of knowledge, interest, or activity.

    a metaphorical sphere or domain of activity, thought, or knowledge.

    Simple

    The discovery was a major breakthrough in the realm of science.

    In context

    Such theoretical questions fall outside the realm of practical politics and are better suited for academic debate.

  2. 02 C1 Advanced LiteraryFormal

    a country or territory ruled by a king or queen.

    a community or territory over which a sovereign rules; a kingdom.

    Simple

    The knights swore to protect the peace of the realm.

    In context

    The monarch sought to expand the borders of the realm through a series of strategic alliances and marriages.

  3. 03 C2 Proficiency Technical Science

    a very large area of the world where specific types of animals and plants live.

    a primary biogeographic division of the Earth's surface, such as the Nearctic or Palearctic.

    Simple

    Australia belongs to a unique biological realm with many animals found nowhere else.

    In context

    Biogeographers divide the terrestrial world into several distinct realms based on the evolutionary history of the flora and fauna found therein.

    bioregioneco zone
  4. 04 C2 Proficiency Technical Science

    the highest level used to group different types of viruses.

    the highest taxonomic rank used in the classification of viruses.

    Simple

    Scientists placed the new virus into a specific realm based on its genetic structure.

    In context

    In viral taxonomy, the rank of realm was established to accommodate the vast genetic diversity that exceeds the traditional kingdom level.

Usage realm of

It's especially relevant in the realm of artificial intelligence, where data center demand driven in part by AI workloads is straining power grids and creating new capacity bottlenecks.

Phys.org· 19 Aug 2026

I’d spent so many years focusing on identifying sounds above ground, and now I had a portal into this earthy realm and a whole new acoustic space.

Aeon· 17 Aug 2026

From Middle English rewme, realme, reaume, from Old French reaume, realme, reialme (“kingdom”), of unclear origins. A postulated *rēgālimen (“domain, kingdom”), Late Latin or Vulgar Latin cross of regimen with rēgālis is usually cited. The modern spelling predominates from around 1600. The modern pronunciation with /l/ is either a spelling pronunciation or influenced by the etymology.

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

This entry
Origin la-vul -
Level C1 · Advanced
Frequency Common
Updated