When adjectives modify nouns, usually they restrict the class of objects that the noun refers to.
A red car is, in particular, an instance of a car.
However, in specialty fields, we often encounter objects named by an adjective+noun combination, which are not (necessarily) actually instances of the object described by the noun itself. An example from mathematics:
A "topology" is a type of mathematical object satisfying certain axioms, whereas a "weak topology" may satisfy only a subset of those axioms. A "weak topology" need not be an instance of a topology. In mathematics, there are even sometimes adjective+noun combinations which refer to objects that are necessarily not instances of the class the noun describes.
Outside of mathematics, I can find only a few examples that are only arguably examples. Usually if I encounter something that looks like this phenomenon, it can be explained away by an archaic meaning of the noun that would turn the adjective+noun combination of the first kind described above, for example:
I have two questions:
- Does anyone know a name for this linguistic phenomenon?
- Are there examples of this phenomenon which are non-technical and can't be turned into the first type described above simply by appealing to an archaic or unusual meaning of the noun?