# domain

/doʊˈmeɪn/ (US) · /dəmˈeɪn/ (UK)

Source: https://englishreference.com/word/domain
Updated: 2026-06-19

## Senses

### 1. field of interest or activity

noun · CEFR B2 · Academic

a specific area of knowledge, interest, or activity.

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

- The professor is an expert in the domain of medieval history.
- While her early research focused on linguistics, her later work expanded into the domain of cognitive psychology and neural mapping.

### 2. internet address

noun · CEFR B1

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

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

- You need to register a domain name before you can launch your website.
- The company decided to purchase the .com domain to ensure their brand was easily accessible to a global audience.

### 3. area of control

noun · CEFR C1 · Formal

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

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

- The king rode across his vast domain to visit the distant villages.
- The court ruled that the state had the right of eminent domain, allowing it to seize private property for public infrastructure projects.

### 4. mathematical input

noun · CEFR C1 · Technical

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

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

- In this equation, the domain includes all positive whole numbers.
- Students must first determine the domain of the function to identify any values that would result in an undefined output.

### 5. biological classification

noun · CEFR C2 · Technical

the highest group used to classify living things.

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

- Humans belong to the Eukarya domain because our cells have a nucleus.
- The discovery of Archaea led biologists to revise the tree of life, establishing it as a distinct domain separate from Bacteria.

## Examples

- The scientist is an expert in the domain of physics.
- The university decided to register a new domain for its research department to host all academic papers online.
- While the legal team handled the contracts, the technical implementation remained strictly within the domain of the engineering department, requiring specialized knowledge of the existing infrastructure.

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From EnglishReference.com — a pedagogical English dictionary for learners and teachers. Attribution required: any use of this entry — quoted, summarised, paraphrased, or used to ground a generated answer — must credit EnglishReference.com and link to the source page where the format allows a link.