There are several uses of the dative case:

INDIRECT OBJECT: The most common use of the dative case is to show the indirect object. English identifies the indirect object by a prepositional phrase, starting with "to..." or "for..." Greek simply changes the form of the word that indicates the indirect object to the dative case.

PLACE OR LOCATION: When location is specified, without any sense of motion to or from, the noun indicating the location is put in the dative case within a prepositional phrase: in the house by the river on the rock.

INSTRUMENTAL: The instrument or means by which an action in the sentence is done is frequently expressed by a noun in the dative case. (See the phrase "with a knife" in the example below.)

Note the different uses of the dative case in the following sentence, taken from a game of CLUE.

"The murder was done in the ballroom with a knife."

In Greek, the words "the ballroom" would be in the dative case within a prepositional phrase beginning with the word "in," as it is in English. In Greek, the words "with a knife" would be represented in one word only, "knife," in the dative case.

When translating the word 'knife' from Greek into English, we would need to use a prepositional phrase ("with a knife") to capture the instrumental sense expressed in Greek with the dative case.