domain

American  

[doh-meyn] / doʊˈmeɪn /

noun

1. a field of action, thought, influence, etc..

   the domain of science.

2. the territory governed by a single ruler or government; realm.

3. a realm or range of personal knowledge, responsibility, etc.

4. a region characterized by a specific feature, type of growth or wildlife, etc..

   We entered the domain of the pine trees.

5. Law. land to which there is superior title and absolute ownership.

6. Biology. a taxonomic category of the highest rank, just above kingdom, grouping together all forms of life having certain fundamental characteristics in common: in the three-domain system of classification adopted by many biologists, separate domains are assigned to the archaea (Archaea), bacteria (Bacteria), and eukaryotes (Eukaryota).

7. Mathematics.

   1. the set of values assigned to the independent variables of a function.

   2. region.

8. Computers.

   1. a group of computers and devices on a network that are administered under the same protocol.

   2. (on the internet) one or more computers or computer networks under the same administrative control, identified by a domain name or any of its discrete parts.

   3. top-level domain.

9. Physics. one of many regions of magnetic polarity within a ferromagnetic body, each consisting of a number of atoms having a common polarity, and collectively determining the magnetic properties of the body by their arrangement.

10. Crystallography. a connected region with uniform polarization in a twinned ferroelectric crystal.

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domain British  

/ dəˈmeɪn /

noun

1. land governed by a ruler or government

2. land owned by one person or family

3. a field or scope of knowledge or activity

4. a region having specific characteristics or containing certain types of plants or animals

5. a park or recreation reserve maintained by a public authority, often the government

6. law the absolute ownership and right to dispose of land See also demesne eminent domain

7. maths

   1. the set of values of the independent variable of a function for which the functional value exists Compare range

      the domain of sin x is all real numbers

   2. any open set containing at least one point

8. logic another term for universe of discourse

   domain of quantification

9. philosophy range of significance (esp in the phrase domain of definition )

10. Also called: magnetic domain.  physics one of the regions in a ferromagnetic solid in which all the atoms have their magnetic moments aligned in the same direction

11. computing a group of computers, functioning and administered as a unit, that are identified by sharing the same domain name on the internet

12. Also called: superkingdom.  biology the highest level of classification of living organisms. Three domains are recognized: Archaea (see archaean ), Bacteria (see bacteria ), and Eukarya (see eukaryote )

13. biochem a structurally compact portion of a protein molecule

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domain Scientific  

/ dō-mān′ /

1. Mathematics The set of all values that an independent variable of a function can have. In the function y = 2 x, the set of values that x (the independent variable) can have is the domain.

2. Mathematics Compare range

3. Computer Science A group of networked computers that share a common communications address.

4. Biology A division of organisms that ranks above a kingdom in systems of classification that are based on shared similarities in DNA sequences rather than shared structural similarities. In these systems, there are three domains: the archaea, the bacteria, and the eukaryotes.

5. Physics A region in a ferromagnetic substance in which the substance is magnetized with the same polarization throughout.

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Other Word Forms

• domanial adjective

Etymology

Origin of domain

First recorded in 1595–1605; from French domaine, alteration (by association with Latin dominium “right of ownership, property”) of Old French demeine, from Late Latin dominicum, noun use of neuter of Latin dominicus “of a master,” equivalent to domin(us) “lord, master” + -icus; dominium, -ic

Explanation

If you have a place that's all your own, somewhere real or in cyberspace that has your name all over it — literally or figuratively — it's your domain. And if you have something you really excel at, that is your domain too. You own it. A domain used to mean only land owned by wealthy people, such as lords in the 15th century, but modern usage is much wider, or has a broader domain in the English language. On the Internet, a domain is a space with a specific address, but a domain can also have a physical address, like a home. It can be a specialty, too, as in, "The main domain of the art school was sculpture," or "She was so good at math that algebra became her domain."

Example Sentences

The military has repeatedly denied involvement in Khan's legal cases or meddling in the civilian domain.

From Barron's • Apr. 12, 2026

These domain walls form interconnected networks throughout the material.

From Science Daily • Apr. 10, 2026

The team had to map the full workflow, document domain expertise, structure internal data, build agents and then verify everything.

From MarketWatch • Apr. 10, 2026

The day after she was sacked, her official portrait was thrown in the trash at the very building that had been her domain.

From Salon • Apr. 9, 2026

“Jefferson sold several young men with a propensity for running away,” Monticello historian Lucia Stanton explains, “in accordance with his policy of ridding his domain of disruptive elements.”

From "In the Shadow of Liberty" by Kenneth C. Davis

Related Words

• realm
• sphere
• territory