realm realm /ˈrɛlm/

noun

1. () A domain in which something is dominant  ( kingdom , land , realm )
   a domain in which something is dominant
    The untroubled kingdom of reason
   the untroubled kingdom of reason
    A land of make-believe
   a land of make-believe
    The rise of the realm of cotton in the south
   the rise of the realm of cotton in the south
   
2. A knowledge domain that you are interested in or are communicating about  ( realm , region )
   a knowledge domain that you are interested in or are communicating about
    It was a limited realm of discourse
   it was a limited realm of discourse
    Here we enter the region of opinion
   here we enter the region of opinion
    The realm of the occult
   the realm of the occult
   
3. The domain ruled by a king or queen  ( realm , kingdom )
   the domain ruled by a king or queen