Final answer:
When a building extends onto another's land, it is usually an encroachment. However, if the government is involved and the land is needed for public use, this process falls under eminent domain, where the owner is compensated.
Step-by-step explanation:
When a building extends onto someone else's land without their permission, it is typically considered an encroachment. Encroachment can lead to legal disputes over property lines and rights. However, in the context provided which mentions the Takings Clause and eminent domain, if a government needs to extend a building or other infrastructure onto private land for public use, it may invoke eminent domain. This process allows the government to take private land for public use, as long as the owner is paid fair compensation. It is not the same as an encroachment, which is unauthorized, but rather a legal process that is followed by the government to obtain private land for projects serving the public interest, such as schools or roads.