Koristnim
Koristnim is a grammatical form associated with the adjective koristan, which means useful or beneficial in several South Slavic languages, including Croatian, Bosnian, Serbian, and Montenegrin. The form koristnim appears in the instrumental singular and is used when the adjective modifies a noun in the instrumental case, typically to indicate that something is useful as a means or in a particular context.
Etymology and morphology are straightforward within the language group. The root korist- derives from the noun
Usage and meaning are largely procedural in nature. In standard written and spoken Croatian, Bosnian, Serbian,
Relation to related terms is close: the noun korist denotes benefit or usefulness, and the related adjectives