domain

/dəˈmeɪn/ (bre, ipa) · /dəʊˈmeɪn/ (ame, ipa) · /dō-ˈmān də-/ (ame, mw)

domain — noun

  • domainsingular
  • domainsplural

1. A specific area of life, work, or thought where a person, group, or organisation

1.名詞B2
釋義

A specific area of life, work, or thought where a person, group, or organisation has authority, responsibility, or influence.

例句

Gabriel's main domain of expertise is artificial intelligence, not graphic design.

collocation: domain of expertise

Serious medical decisions belong firmly within the domain of qualified doctors.

phrase: within the domain of

同義詞
  • field

    less formal, more common in everyday use

  • realm

    more abstract or imaginative in tone

  • sphere

    often suggests social or interpersonal scope

  • arena

    implies a competitive or active environment

文法句型

someone's domain

the domain of something

用法筆記

Frequently used with possessive determiners (my domain, her domain) or in the prepositional phrase 'within the domain of'.

常見錯誤

❌I work in this domain' (vague).
✅I work in the domain of software security.
💡Specify what kind of domain when referring to a professional field.
❌This problem is out of my domain' (unnatural).
✅This problem is outside my area of expertise.
💡For everyday speech, 'area of expertise' or 'field' is more natural than 'domain'.

2. An organised section of the internet identified by a shared ending in web addres

2.名詞B1
釋義

An organised section of the internet identified by a shared ending in web addresses, such as .com, .org, or .tw.

例句

The company bought the domain "ecopack.shop" for its new online store.

collocation: bought the domain

Websites ending in ".org" belong to the domain of non-profit organisations.

同義詞

文法句型

register + domain

domain + name

用法筆記

Commonly paired with 'register', 'buy', 'own', or 'transfer'. In informal speech, 'domain' is often short for 'domain name'.

常見錯誤

❌I created a new domain for my blog.
✅I registered a new domain name for my blog.
💡You register or buy a domain; you do not 'create' one.

3. The complete set of numbers or values that can be used as inputs for a particula

3.名詞C1
釋義

The complete set of numbers or values that can be used as inputs for a particular mathematical function.

例句

The domain of the square-root function includes only non-negative numbers.

pattern: the domain of + [function]

Indra learned how to find the domain of a logarithmic equation in class.

同義詞
反義詞
  • range

    the set of output values produced by a function

文法句型

the domain of + function

用法筆記

Often contrasted with 'range', which refers to the set of output values. A common exam question asks students to identify both the domain and the range of a given function.

常見錯誤

❌The range of the function is all positive numbers' (when the speaker means inputs).
✅The domain of the function is all positive numbers.
💡Domain = possible inputs; range = possible outputs.

4. A physical territory, such as land or a region, that is governed or owned by a p

4.名詞B2
釋義

A physical territory, such as land or a region, that is governed or owned by a particular ruler, state, or authority.

例句

The Roman domain once stretched from Britain all the way to North Africa.

possessive: the Roman domain

The emperor sent soldiers to protect his eastern domain from enemy attacks.

possessive: his eastern domain

同義詞
  • territory

    more common in modern political and legal contexts

  • realm

    often used for kingdoms or abstract areas

  • dominion

    formal or historical, emphasising ruling power

文法句型

possessive + domain

the domain of + ruler/state

用法筆記

Frequently appears in historical writing about empires, kingdoms, and colonial territories. Less common in modern political language, where 'territory' or 'jurisdiction' is preferred.

常見錯誤

❌This desk is my domain' (when casually claiming a workspace).
✅This is my corner of the office.
💡Sense 1 (area of interest) is more natural for casual personal space than this territorial sense.

5. In biology, the largest and most general category used to organise all living th

5.名詞C1
釋義

In biology, the largest and most general category used to organise all living things, sitting above kingdoms in the classification hierarchy.

例句

All animals, plants, and fungi belong to the domain called Eukarya.

pattern: belong to the domain + [name]

Scientists divide all life into three domains: Bacteria, Archaea, and Eukarya.

同義詞

文法句型

the + number + domains of life

domain + name

用法筆記

Typically encountered in biology textbooks and scientific writing. The three-domain system (Woese, 1990) replaced the older five-kingdom model. Learners at CEFR B2 or below are more likely to encounter 'kingdom' than 'domain'.

常見錯誤

❌Kingdom and domain mean the same thing in biology.
✅Domain is the broader category that sits above kingdom.
💡Domain is the highest rank; kingdom is one level below it.