Case (grammar)

A "case" in grammar is like a little box that a noun or pronoun fits into to show people reading or listening to the sentence what job that word is doing. There are different cases for different jobs, like the "nominative" case for when a noun is the subject of a sentence (the person or thing doing the action), the "accusative" case for when a noun is the object of a verb (the thing being acted upon), and the "genitive" case for when a noun shows possession (like "the cat's toy").

So just like when you put your toys away in different boxes based on what they are used for (like putting your stuffed animal in the toy box and your blocks in the block box), words in a sentence also have their own special boxes based on what they are doing in the sentence. This can help make sentences easier to understand because readers or listeners can quickly figure out what each word is doing.