From WordNet (r) 3.0 (2006):
domain
n 1: a particular environment or walk of life; "his social
sphere is limited"; "it was a closed area of employment";
"he's out of my orbit" [syn: sphere, domain, area,
orbit, field, arena]
2: territory over which rule or control is exercised; "his
domain extended into Europe"; "he made it the law of the
land" [syn: domain, demesne, land]
3: (mathematics) the set of values of the independent variable
for which a function is defined [syn: domain, domain of a
function]
4: people in general; especially a distinctive group of people
with some shared interest; "the Western world" [syn: world,
domain]
5: the content of a particular field of knowledge [syn:
knowledge domain, knowledge base, domain]