What is the meaning of domain?

noun

• A particular environment or walk of life.
  • usage: "his social sphere is limited"; "it was a closed area of employment"; "he's out of my orbit"
  • synonyms: sphere, area, orbit, field, arena
• Territory over which rule or control is exercised.
  • usage: "his domain extended into Europe"; "he made it the law of the land"
  • synonyms: demesne, land
• Mathematics) the set of values of the independent variable for which a function is defined.
  • synonyms: domain of a function
• People in general; especially a distinctive group of people with some shared interest.
  • usage: "the Western world"
  • synonyms: world
• The content of a particular field of knowledge.
  • synonyms: knowledge domain, knowledge base