* Subjects restricted by scope: This refers to situations where the grammatical subject of a sentence is limited in its reference. For example:
* Specific individuals: "The *students* in my class are hardworking." (The subject "students" is limited to the students in a specific class, not all students.)
* Specific time frames: "The *sun* shone brightly yesterday." (The subject "sun" refers to the sun's state only on a specific past day.)
* Specific locations: "The *birds* in that tree are singing." (The subject "birds" is limited to those in a particular tree.)
* Specific types: "The *red cars* are parked over there." (The subject is limited to red cars, excluding cars of other colours.)
* Subjects in a limited domain of discourse: This refers to subjects being discussed within a specific context or field of study. For example, a physics paper might only deal with the subject of "particle physics," limiting its subject matter drastically.
* Subjects with limited agency or control: This is a more interpretive idea. It could refer to subjects in a sentence who have little power or influence over the situation described. For instance, "The *child* was hit by a car." The child has little agency in the event. This isn't a formal grammatical term, but a potentially useful analytical one in certain contexts (e.g., literary analysis).
* Subjects with limited grammatical possibilities: This is unlikely, as most subjects, grammatically, can take on a wide variety of predicate constructions.
To understand what "limited subjects" means, you need to examine the specific context where you encountered the term. Provide the context, and I can give you a more precise answer.