Which term refers to unplanned housing built without legal permission?

The term that refers to unplanned housing built without legal permission is squatter settlements. These areas typically arise when people occupy land or property that they do not own or have permission to use, often due to rapid urbanization and a lack of affordable housing options. Squatter settlements can often develop on lands that are unsuitable for living, such as on the edges of cities or in hazardous regions.

The term "slums" generally refers to urban areas characterized by substandard housing and inadequate living conditions, often associated with poverty and lack of basic services, but it does not specifically indicate how the housing was acquired. "Shanty towns" is similar, often used interchangeably with squatter settlements, but it tends to emphasize the makeshift nature of the structures rather than the legal status of the land. "Cage homes" specifically refers to a type of extremely small housing found in some urban areas, particularly in Hong Kong, and does not apply broadly to unplanned or illegal housing. Squatter settlements is the most precise term for the situation of informal housing constructed without legal permission.