Polish/Instrumental case

Narzędnik (Instrumental)
The instrumental case in Polish is used in the following situations:
 * 1) Indicates the object of a sentence when it is used with certain verbs, prepositions, or phrases.
 * 2) * Idę z Piotrem. - I'm going with Piotr. (Piotrem is in the instrumental case)
 * 3) Used for sentences of the type "to jest …" when the subject is not a pronoun.
 * 4) * To jest moim domem. - This is my house. (moim domem is in the instrumental case)
 * 5) Indicates the means or way something is done.
 * 6) * Piszę długopisem. - I'm writing with a pen. (długopisem is in the instrumental case)

The instrumental case answers the questions with who? (z kim?) and with what? (z czym?).

Singular
The singular form of the instrumental case is formed by adding specific endings to the nominative form.

Noun Declension
See Polish/Hard and soft consonants

Plural
In the plural form, nouns in Polish are declined based on gender, either as virile (masculine personal) or nonvirile (masculine animate, masculine inanimate, feminine, and neuter).