large dwelling house

A mansion is a large and often luxurious house. It can be big enough for an owner, their family, and their many servants. One of the definitions is a large, imposing house. It was originally the called the same as a manor house but when similarly large houses were built in cities they were called "mansions". A "country house" is a common type of mansion in England.

The Breakers, a famous mansion from Newport, Rhode Island