Deficit area
An area formally identified as falling short on a defined standard, such as green space or cooling, which makes it a place planning can act on.
A deficit area, in German Defizitgebiet, is an area identified as falling below a defined standard. The standard is usually an accessibility or provision threshold: too little green space within reach, too much heat exposure, not enough cooling. Once a threshold is set, the areas that fail it can be drawn as polygons on a map.
The point of the designation is that it converts a statistic into a place. A number in a report is hard to act on, while an area with a boundary has an address, a district, residents and a responsible authority. That makes it something a planning process can attach a measure to, and something a resident can see.
It follows that the threshold does the real work, and the threshold is a decision. Whoever defines the standard defines which areas count as deficient, so the standard should be stated alongside the map, along with the source it comes from. A deficit area with an unexplained threshold is an assertion rather than a finding.