in-law unit
n.— «As part of sweeping zoning changes, the city council will decide next month whether to increase the number of homesites that could add garage apartments or cottages, commonly referred to as granny or in-law units.» —“P.A. considers allowing more ‘granny’ units” by Kellie Schmitt, Dan Stober Mercury News (San Jose, California) Mar. 27, 2005. (source: Double-Tongued Dictionary)