/ dəˈmeɪn; dəʊ-; NAmE doʊ-/ noun
1.
an area of knowledge or activity; especially one that sb is responsible for :
The care of older people is being placed firmly within the domain of the family.
Physics used to be very much a male domain.
—see also public domain
2.
lands owned or ruled by a particular person, government, etc., especially in the past :
The Spice Islands were within the Spanish domains.
3.
( computing ) a set of websites on the Internet which end with the same group of letters, for example '.com', '.org'
4.
( mathematics ) the range of possible values of a particular variable
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WORD ORIGIN
late Middle English (denoting heritable or landed property): from French domaine , alteration (by association with Latin dominus lord) of Old French demeine belonging to a lord, from Latin dominicus , from dominus lord, master.