A secondary dwelling unit built on a residential lot — a complete independent home with its own kitchen, bathroom, and entrance, sharing the lot with the primary residence.
California state law (post-AB-2221, AB-976, AB-1033) requires every city to allow at least one ADU on every single-family lot. Sometimes called granny flats, in-law units, casitas, secondary dwellings, or backyard cottages — all the same thing under the law.
Part of the BackyardADU California ADU Glossary — plain-English definitions of the regulatory, construction, and financing terms you'll encounter during a California ADU project.