A mansion is a large dwelling house.
 
The word itself derives (through Old French) from the Latin word mansio "dwelling", an abstract noun derived from the verb manere "to dwell". The English word "manse" originally defined a property large enough for the parish priest to maintain himself, but a mansion is no longer self-sustaining in this way (compare a Roman or medieval villa). 'Manor' comes from the same root— territorial holdings granted to a lord who would remain there— hence it is easy to see how the word 'Mansion' came to have its meaning.
 
Mansions built during the last and present centuries usually have specially designed rooms meant to accommodate leisure activities of a particular kind. Many will have a conservatory or greenhouse, while others will have an infinity pool or a home theater. Some have all of these features. The relative importance of these specially designed rooms changes with the times: At the beginning of the 20th century no true mansion would have been built without a room to house a private library or office, while at the beginning of the 21st century the presence of a room designed for a home theater or cinema is a must. Most recently, mansions have been built with integrated domotics.
 
A modern mansion today may not necessarily be limited to a single house standing alone, but like Nero's DomusAurea on the Palatine Hill, Rome, compounds, or a grouping of larger houses. The Kennedy Compound is an example of one family building surrounded by large houses on a single plot.