Breakdown of Мой старший сын интересуется современным искусством.
мой
my / mine
современный
modern
искусство
art
сын
son
Questions & Answers about Мой старший сын интересуется современным искусством.
Why is "in modern art" translated using the Instrumental case (современным искусством)?
The verb интересоваться (to be interested in) always requires the object of interest to be in the Instrumental case. Even though in English we use the preposition "in", in Russian you just use the bare Instrumental case without any prepositions here.
The lesson is about using the Instrumental case for tools. Is "modern art" considered a tool in this sentence?
No. While the bare Instrumental is used to show the tool an action is done with (like eating with a spoon), it is also grammatically required by certain verbs. Verbs like интересоваться (to be interested in) and заниматься (to be occupied with) just demand the Instrumental case for their objects, entirely unrelated to tools.
How do we get the ending -ым on современным?
The dictionary form is современный (modern). It is describing the neuter noun искусство (art). In the Instrumental case, both masculine and neuter adjectives take the ending -ым (or -им after certain letters).
Why does the verb интересуется end in -ся?
The base verb is интересовать, which means to interest someone else. By adding the reflexive particle -ся, the action turns back on the subject, changing the meaning to "to be interested". Since the subject сын (son) is a "he", we use the "he" conjugation интересует, plus -ся, giving us интересуется.