What is the term for land that has been previously developed and is now abandoned?

The term for land that has been previously developed and is now abandoned is "Brownfield sites." This term specifically refers to previously used land, particularly in urban areas, where the reuse or redevelopment may be complicated by the presence of hazardous substances or pollutants. Brownfield sites often require assessment and cleanup before they can be successfully redeveloped, making them significant in discussions of urban planning and redevelopment initiatives.

The other terms mentioned have different meanings. Urban renewal sites refer to areas undergoing comprehensive redevelopment to improve living conditions and infrastructure, often in revitalized urban spaces. Greenfield sites are undeveloped lands, usually in rural areas, that have never been built on, making them ideal for new developments. Vacant properties, while they may refer to abandoned buildings or lots, do not specifically imply that the site was previously developed and may include structures awaiting sale or rent that are not necessarily contaminated or complicated by urban decay issues.