English Reference
noun

domain

n.
US /doʊˈmeɪn/ UK /dəmˈeɪn/ do·main UK spelling domain's, domain's

  1. 01 B2 Upper Intermediate Academic

    a specific area of knowledge, interest, or activity.

    a sphere of activity, influence, or expertise; often used in academic contexts to describe a subject area.

    Simple

    The professor is an expert in the domain of medieval history.

    In context

    While her early research focused on linguistics, her later work expanded into the domain of cognitive psychology and neural mapping.

  2. 02 B1 Intermediate Computing

    a set of words used to identify a website on the internet.

    a series of alphanumeric strings separated by periods that identifies a specific location on the internet.

    Simple

    You need to register a domain name before you can launch your website.

    In context

    The company decided to purchase the .com domain to ensure their brand was easily accessible to a global audience.

    URLweb address
  3. 03 C1 Advanced Formal Law

    an area of land that is owned or controlled by one person or government.

    a territory over which dominion is exercised; a district or region under a particular jurisdiction.

    Simple

    The king rode across his vast domain to visit the distant villages.

    In context

    The court ruled that the state had the right of eminent domain, allowing it to seize private property for public infrastructure projects.

  4. 04 C1 Advanced Technical Math

    the set of all possible numbers that can be put into a mathematical function.

    the set of all possible values of an independent variable for which a function or relation is defined.

    Simple

    In this equation, the domain includes all positive whole numbers.

    In context

    Students must first determine the domain of the function to identify any values that would result in an undefined output.

  5. 05 C2 Proficiency Technical Science

    the highest group used to classify living things.

    the highest taxonomic rank of organisms in the three-domain system, sitting above the kingdom level.

    Simple

    Humans belong to the Eukarya domain because our cells have a nucleus.

    In context

    The discovery of Archaea led biologists to revise the tree of life, establishing it as a distinct domain separate from Bacteria.

Usage define domain · given domain · multiple domain

When asked in parliament in 2024 , external affairs minister S Jaishankar said that information is not in public domain and that exports of military products are guided by “national interest”.

The Guardian· 11 Aug 2026

Archaea and bacteria are two of the three domains of life , and these microbes arose early in Earth’s history.

Smithsonian Magazine· 5 Aug 2026
This entry
Level C1 · Advanced
Frequency Common
Updated