1. особняк currently denotes a private detached house, usually occupied by one family which, in the past, would have been built by wealthy members of society; особняки were usually located in prestigious areas of a town or city; the grander особняки were also sometimes called 'палац'

2. the country equivalent of особняк would have been садиба - a house to which a farmstead would have been attached.

особа - individual, person