Wiktionary
n. (context grammar English): noun case used to indicate means. It answers the question "how?", and in English, this is usually expressed by the prepositional phrase '''by means of''', as in "by means of the house". Languages that use the instructive case include Finnish and (rarely) Estonian.
Wikipedia
In the Finnish language, the instructive case has the basic meaning of "by means of". It is a comparatively rarely used case, though it is found in some commonly used expressions, such as omin silmin → "with one's own eyes".
In modern Finnish, many of its instrumental uses are being superseded by the adessive case, as in "minä matkustin junalla" → "I travelled by train."
It is also used with Finnish verbal second infinitives to mean "by ...ing", e.g. "lentäen" → "by flying", "by air" ("lentää" = "to fly").
In Estonian, the instructive case (Estonian: viisiütlev) also exists, but only in some words. (f.e: "jalgsi" - "on foot", from "jalg" - foot)
In Turkish, the suffix -le is used for this purpose. Ex: Trenle geldim "I came via train".
Category:Grammatical cases
Usage examples of "instructive case".
For the indignant and Whoever perpetually tears and lacerates with his own teeth himself (or as a substitute, the world, or God, or society) may indeed, morally speaking, stand higher than the laughing and self-satisfied satyr, but in every other sense they are a more ordinary, more indifferent, and less instructive case.