domain

American  

[doh-meyn] / doʊˈmeɪn /

noun

• domains
  plural

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.

---

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

---

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.

---

Other Word Forms

Derived Forms

• domanial
  adjective

Inflected Forms

Nouns

• domains
  plural

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; see origin at 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

See Examples For:

domain domains

I was more secure in my own domain.

From Salon ● Aug. 24, 2026

Cyber security expert Dr Daniel Thomas, of the University of Strathclyde, said the incident was an example of "domain squatting".

From BBC ● Aug. 22, 2026

Does your company shape AI around domain expertise?

From The Wall Street Journal ● Aug. 19, 2026

It was registered privately, so it is not possible to see who exactly owns the website’s domain.

From Los Angeles Times ● Aug. 19, 2026

“I shouldn’t have made that promise, Bob. I just wanted—” I point to Stella’s domain, and for a moment, it seems like I’ve forgotten how to breathe.

From "The One and Only Ivan" by Katherine Applegate

US law enforcement on Tuesday announced the seizure of internet domains allegedly used by Chinese hackers to target government agencies and critical infrastructure.

From Barron's ● Aug. 26, 2026

For many companies, especially those in specialty domains like cybersecurity and material science, there’s the concern that AI providers could become competitors, Briski said.

From The Wall Street Journal ● Aug. 11, 2026

To be successful in achieving Bessent’s objectives, the U.S. government will need a comprehensive framework for industrial policies that treats geoeconomics, AI and energy as intertwined domains, not as separate silos.

From MarketWatch ● Aug. 5, 2026

These technologies allowed the researchers to identify six distinct tissue domains that appeared to represent different stages of Alzheimer's progression.

From Science Daily ● Jul. 26, 2026

These tiny, fractious domains endured for more than a thousand years.

From "1491" by Charles C. Mann

Related Words

• realm
• sphere
• territory