Meaning of DOMAIN in English

do ‧ main AC /dəˈmeɪn, dəʊ- $ də-, doʊ-/ BrE AmE noun [countable] formal

[ Date: 1400-1500 ; Language: French ; Origin: domaine , from Latin dominus 'lord' ]

1 . an area of activity, interest, or knowledge, especially one that a particular person, organization etc deals with

outside/within the domain of something/somebody

This problem is outside the domain of medical science.

Looking after the house was viewed as a woman’s domain.

⇨ ↑ public domain

2 . an area of land owned and controlled by one person or government, especially in the past:

the extent of the royal domain

3 . technical the set of possible quantities by which something can vary in mathematics

4 . a domain name

Longman Dictionary of Contemporary English.      Longman - Словарь современного английского языка.