1. a particular environment or walk of life

Similar word(s): area, arena, field, orbit, sphere

Definition categories: state, environment

2. territory over which rule or control is exercised

- his domain extended into Europe

Similar word(s): demesne, land

Definition categories: location, region

3. (mathematics) the set of values of the independent variable for which a function is defined

Definition categories: group, set

4. people in general; especially a distinctive group of people with some shared interest

Similar word(s): world

Definition categories: group, class, stratum

5. the content of a particular field of knowledge

Definition categories: thought, content

Sentences with domain as a noun:

- The king ruled his domain harshly.

- Dealing with complaints isn't really my domain: get in touch with customer services.

- His domain is English history.