Here are a few ways to form the possessive case:
* Singular nouns: Add an apostrophe and an "s" (e.g., the dog's bone).
* Plural nouns ending in "s": Add only an apostrophe (e.g., the dogs' bones).
* Plural nouns not ending in "s": Add an apostrophe and an "s" (e.g., children's toys).
Let me know if you have any other grammar questions!