Final answer:
The double dative in Latin uses two uses of the dative case: the Dative of Purpose, indicating a beneficiary or purpose, and the Dative of Reference, marking a person or thing in whose interest something is done. These can be combined in a single phrase.
Step-by-step explanation:
The double dative, a concept in Latin, refers to two different uses of the dative case in a single construction. These two uses are known as the Dative of Purpose (or 'dative for') and the Dative of Reference (or 'dative to').
The Dative of Purpose denotes a beneficiary or purpose. For example, in the sentence 'Dedi librum amico' ('I gave the book for a friend'), 'amico' serves the purpose of identifying the person for whom the action was performed.
The Dative of Reference denotes a person or thing in whose favor, interest, or against which, something is done. In the sentence 'Hoc mihi est utili' ('This is useful to me'), 'mihi' stands as a Dative of Reference, pointing towards to whom the action or situation is useful.
Inputting these two uses in a single phrase results in construction known as the double dative - for instance, 'Dedi librum amico usui' : I gave the book to my friend for use.'
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