Final Answer:
The case used to show the instrument by which something is done is known as the ablative case.
Step-by-step explanation:
In linguistic terms, cases are grammatical categories that indicate the syntactic or semantic role of a noun within a sentence.
The ablative case specifically denotes the means or instrument by which an action is performed.
When expressing the tool, method, or instrument used to carry out an action, the ablative case comes into play.
For example, in the sentence "He wrote with a pen," the noun representing the pen would be in the ablative case.
It serves to highlight the instrument used in the action of writing. This case is essential in various languages, including Latin and some Slavic languages, where it plays a crucial role in conveying the nuances of relationships between objects and actions.
Understanding the ablative case is valuable for accurate language usage, especially in contexts where precision in indicating the means or instrument of an action is essential.
In summary, the ablative case is employed to showcase the instrument by which something is done in linguistic expressions.