The case of means or association.
The Instrumental of Means
Usually this use expresses impersonal means. It is closest to the root idea of the case. This use may be determined by the ability to use the words “by means of” or “by” in the translation. Sometimes “with” may be used in translation with the idea of association. (cf. The Instrumental of Agency below).
The Instrumental of Cause
This use expresses cause, motive, or occasion. It goes behind the intermediate means to the original cause or factor producing a result. It may refer to an external cause and thus a motive. This use is determined by the ability to use the word “because” in the translation.
The Instrumental of Manner
This use indicates the method by means of which the action is carried out. A circumstance accompanying the action of the verb is indicated. This use may answer the question “how?” or “in what manner?”.
The Instrumental of Measure
The Instrumental is used to express measure in comparative phrases. Two points of time or space are separated by means of an intervening distance. It is used chiefly with reference to time in the N.T. (The locative indicates a definite point in time. The Instrumental indicates two points separated by an interval of time.).
The Instrumental of Association
The word in the Instrumental indicates that person(s) or thing(s) which accompany or take part in the action of the verb. The key to this use is to find a second party who furnishes the means of association. It often occurs with compounds of σύν. This use, which is also referred to as the “Commutative,” occurs frequently in the N.T. It will be translated “with,” or “together with”.
Instrumental of Agency
The Instrumental on rare occasions is used to express personal agency rather than impersonal means. In these instances, the verb will be in the middle or passive voice. This use could just as well be included under the Instrumental of Means.
The Instrumental with Verbs of Likeness
In this use, there is one word associated with another to illustrate it. The two correspond figuratively.
The Instrumental with Prepositions
The instrumental is used with three prepositions, ἐν, ἃμα and σύν.