Okay kiddo, have you ever noticed how sometimes we use different words to describe what different things do or how they’re involved in a situation?
For example, sometimes we say “I write with a pen” and sometimes we say “I write a letter” without mentioning the pen at all. When we want to talk about the thing we use to do an action, like the pen in that first sentence, and what it’s doing for us, we use a special case called the instrumental case.
It’s like a tool we use to help us explain our sentence better! So when we’re talking about the instrument that’s helping us do something, it gets its own special ending so we know that it’s important. In some languages, like Russian or Latin, you might see words change their endings based on whether they’re in the instrumental case or not.
Thanks for asking such a cool question!