Inherent case

Inherent case is Case which is dependent on theta-marking (as opposed to structural case). Also 'oblique case'. Usually Genitive, Dative, and Partitive are considered inherent case.

Example
the assignment of genitive case by a noun is inherent, hence must coincide with theta-marking. This implies that a noun cannot be the case-assigning head in an ECM construction, and no Raising to Subject in an NP is possible. Hence the illformedness of (i) and (ii).

(i)  * John's belief [ Mary's/of Mary to be a spy ] (ii) * John's appearance [ t to be a spy ]

Also, case is called inherent if its assignment is an idiosyncratic property of the assigning head. EXAMPLE: in German the verb helfen (to help) assigns Dative to its NP object, instead of (structural) Accusative.

Link
Utrecht Lexicon of Linguistics