What term is used to describe an area of land that has been previously built on and is no longer in use?

The term that accurately describes an area of land that has been previously built on and is no longer in use is "brownfield site." Brownfield sites typically refer to land that was previously developed but may now be contaminated or underused. These sites often require remediation before they can be redeveloped for new purposes, such as residential, commercial, or recreational areas.

In contrast, "derelict land" generally refers to land that has been abandoned and is in a state of disrepair, which can include brownfield sites but is not exclusive to them. "Reclaimed land" typically refers to land that has been restored or improved for various uses, often after being degraded or used for industrial purposes. "Vacant lot" usually denotes a piece of land that is empty and may not necessarily have had previous development or usage. Understanding the distinctions among these terms is essential in the context of urban planning and land management.