# domain

Pronunciation: say "doh-MAYN" US /doʊˈmeɪn/, UK /dəʊˈmeɪn/; AUS say "duh-MAYN" /dəʉˈmæɪn/

## Noun

1. A field or sphere in which a person has activity, influence, or expertise.
   - Simple: An area of knowledge, work, or skill that a person deals with.
   - _Constitutional law lies outside my domain, but I can recommend a specialist._
   - _Climate policy has become the domain of economists as much as scientists._
2. An area of land that one particular person or organization owns or has control over.
   - Simple: An area of land that one person, family, or group owns and controls.
   - _The duke expanded his domain through marriage and conquest._
   - _These islands remained the domain of a trading company for two centuries._
3. A DNS name, especially a delegated one that stands for itself together with all of its subdomains.
   - Simple: A name that identifies a website or group of computers on the internet.
   - _The company moved its email and website onto a single domain._
   - _Administrators renewed the domain shortly before it was due to expire._
4. A set of topics, subjects, or items that are connected to one another and treated as a group.
   - Simple: A group of things, topics, or subjects that are connected to each other.
   - _Researchers grouped the survey items into three broad domains._
   - _Vocabulary and grammar belong to the same domain of language learning._
5. In mathematics, the complete set of input values, or arguments, for which a given function has a defined output.
   - Simple: The full set of input values a function is allowed to work with.
   - _To find the domain, exclude any inputs that make the denominator zero._
   - _Two functions sharing a domain can be added pointwise across those inputs._
6. In biology, the top level in the classification of living things, ranking above kingdom; the three-domain system recognizes Bacteria, Archaea, and Eukaryota.
   - Simple: The biggest group scientists use to sort living things, ranking above kingdom.
   - _Carl Woese proposed that life be split into three domains rather than five kingdoms._
   - _Each domain is defined largely by features of ribosomal RNA._
7. In biology, a distinct folded region of a protein molecule that carries out its own function, or the corresponding region of a chromosome.
   - Simple: A folded part of a protein that carries out its own special job.
   - _The enzyme's catalytic domain sits near its membrane anchor._
   - _Mutations in this domain disrupt the protein's ability to bind its target._
8. A small region of a magnetic material within which the magnetization points in a single consistent direction.
   - Simple: A tiny area inside a magnetic material where the magnetism all points one way.
   - _Applying a field aligns each domain along the same axis._
   - _As the magnet cooled, neighboring domains locked into alignment._
9. A collection of DNS or DNS-like names made up of a delegated name together with all of its subdomains.
   - Simple: A group of internet names made up of one main name and all the names under it.
   - _Migrating the entire domain meant updating hundreds of subdomain records._
   - _Their domain spans the root name and all the hosts registered beneath it._
10. The collection of networked computers identified together by a shared domain name.
   - Simple: The group of computers that share one internet name.
   - _The administrator added three new servers to the domain last week._
   - _Every machine on the domain authenticates against the same central server._
11. A body of information covering a network grouping, the computers named within that grouping, and the network where those computers reside.
   - Simple: A set of stored facts about a group of computers and the network they use.
   - _Engineers queried the domain to retrieve the configuration of each registered host._
   - _The domain holds the naming records, machine details, and network data in one place._
12. An open and connected set within a topological space, such as the interval (0,1) inside the real numbers.
   - Simple: In math, a connected group of points that has no edge, like the numbers between 0 and 1.
   - _The function is analytic on a domain that excludes its boundary points._
   - _Mathematicians often prove a result on a single connected domain before extending it._
13. A ring containing no zero divisors: one in which the product of two nonzero elements is never zero.
   - Simple: In math, a system where multiplying two non-zero values never gives zero.
   - _The integers form a domain because no two nonzero integers multiply to zero._
   - _Proving a ring is a domain requires showing it has no zero divisors._
14. A piece of technical metadata that defines a data item's type, characteristics, name, and intended use.
   - Simple: Information that describes a piece of data: its type, name, and how it is used.
   - _The data model defines a domain for every field, specifying its type and allowed values._
   - _Analysts reviewed each domain to confirm the format and usage of incoming records._
15. A region showing more or less uniform mineralization.
   - Simple: An area of rock where the minerals are spread out in much the same way throughout.
   - _The survey identified a domain rich in copper across the valley floor._
   - _Geologists mapped several domains, each with its own mineral signature._
16. A small magnetized region used as a data storage element in bubble memory.
   - Simple: A tiny magnetic spot used to store one bit of data in an old type of computer memory.
   - _In bubble memory, the presence or absence of a domain encodes a binary digit._
   - _Engineers moved each domain along the chip to read the stored data._
17. The set of input values for which a function or relation is defined: the first coordinates of the ordered pairs that make up the relation.
   - Simple: In math, all the input values that a function is allowed to take.
   - _The function's domain excludes zero, since division by zero is undefined._
   - _To define the relation fully, they specified both its domain and its range._

## Origin

This word comes from Middle English demayne ("rule"), from Old French demeine/domaine ("power"), which came from Latin dominium ("property, right of ownership"), itself from dominus ("master, proprietor, owner"). It is a doublet of demesne and domino.

Source: DictionaryAI, https://dictionaryai.com/define/domain (written from Wiktionary data, CC BY-SA 4.0: https://creativecommons.org/licenses/by-sa/4.0/).