An illegal extension of a building onto a neighbor's property is referred to as?

An illegal extension of a building onto a neighbor's property is referred to as encroachment. This term describes a situation where a structure, such as a fence or part of a building, physically intrudes upon another person's land without permission. Encroachment is typically unintentional but can lead to legal disputes, as it infringes on the property rights of the neighboring landowner.

In contrast, adverse possession is a legal doctrine that allows a person to claim ownership of land under certain conditions, usually after occupying it openly and continuously for a specific period. Easement by prescription involves the right to use someone else's property for a specific purpose, acquired through long-term use without permission. A setback violation refers to the breach of regulations concerning the required distance a building must be set back from property lines or roads, which is more related to zoning laws than to encroachments on an adjoining property. Each of these terms describes different legal concepts, but encroachment specifically addresses unauthorized extensions onto another's land.