Old English retains traces of the instrumental case, but for the most part that too has fallen together with the dative. In view of its diverse origins, it should be no surprise that the dative case has a variety of functions. Of these, the easiest for the speaker of Modern English to understand is that of object of a preposition. With other prepositions the case may be either dative or accusative, depending on the writer's dialect or the meaning of the preposition . Here the dative signifies that one is in some way interested in the outcome of an action.
Some verbs have their direct objects in the dative case.
But in this matter it is sufficient for the student to be guided by modern usage and leave the technical aspects to the linguists. Often the dative of possession may also be interpreted as a dative of interest. The dative that expresses inequality is rare enough that beginners probably should not worry about it. Instrument, means, manner. These senses of the dative overlap, and so are grouped together here.