The Russian Instrumental Case is used to show the instrument - or in other words, how the action is carried out.
Like all cases in the Russian language, the easiest way to determine how to use the Instrumental case is to ask the key questions associated with the case. So, in other words, when you are forming the sentence, first ask yourself the questions:
(1) With what, or by whom, is the action done? Or...
(2) Who/what am I proud of?
The answer to these questions will tell you which nouns require the Instrumental case. When in the Instrumental case, nouns drop their 'regular' endings, and are replaced by the corresponding endings shown in the table below.
The table outlines the typical endings used, as well as the relevant endings that apply to any adjectives linked to the noun. Further, we have given some specific examples highlighting the word endings so you can see how the Instrumental case works.