What is referred to as any non-natural structure built on or affixed to land?

The term that describes any non-natural structure built on or affixed to land is "Improvement." Improvements include structures such as buildings, fences, and roads that have been added to the land to enhance its value or utility. This concept is essential in real estate because understanding what constitutes an improvement can influence property valuation, land use planning, and zoning regulations.

In the context of real estate, improvements are often distinguished from the land itself, which is a natural resource. The significance of improvements lies in their ability to increase the functionality and marketability of the property. This clarity is particularly useful in transactions, appraisals, and assessments of property taxation.

Other options like "Property" are broader and may refer to both land and improvements combined. "Land" typically refers only to the natural surface of the earth and its features. "Real Estate" denotes a broader category that includes both land and improvements but does not specifically focus on the non-natural structures that have been built on the land. Therefore, the specific term "Improvement" accurately captures the essence of non-natural structures associated with land.