1. (

• sphere ,
• domain ,
• area ,
• orbit ,
• field ,
• arena

) 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" ;

2. (

• domain ,
• demesne ,
• land ,

) territory over which rule or control is exercised; "his domain extended into Europe"; "he made it the law of the land" ;

3. (

• domain ,
• domain_of_a_function

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

4. (

• world ,
• domain

) people in general; especially a distinctive group of people with some shared interest; "the Western world" ;

5. (

• knowledge_domain ,
• knowledge_base ,
• domain

) the content of a particular field of knowledge ;