Here's something that might help: The genitive usually refers to possession by or close association with one individual person or thing. The 'of' construction is sometimes a more formal version of this, used when the genitive might sound awkward or ambiguous, or when the situation needs to be 'spelled out' more clearly. A compound noun is different. It always tells you what KIND of thing something is. As a formula, an 'xy' is always a specific type of y, and the 'x' part of it distinguishes it from other types of y. For example, a blanket factory might produce wool blankets, cotton blankets and polyester blankets. Here we have compound nouns where the different kinds of blankets are distinguished by their materials. You could also use compound nouns to distinguish between the products by specifying the function, destination or end user ...hospital blankets, baby blankets, picnic blankets or dog blankets. What is a 'dog blanket'? It's a different kind of blanket from other blankets. Dog owners buy dog blankets to put in dog baskets. Here we have three compound nouns (xy) and in each case the first noun (x) distinguishes it from other kinds of y. In general, dog owners are different from cat owners, and dog baskets are different from shopping baskets. So what about the genitive? Here are some examples: What should you do if you come across a lost dog? You should try to find the dog's owner or the owner of the dog. This is the specific owner which is associated with ( or 'belongs to') that individual dog. What should you do if you're staying in a friend's house and you're cold at night? You should go and find a blanket. But be careful to not to take the dog's blanket from the dog's basket, as it might be rather smelly and nasty. Here we're talking about the specific blanket and specific basket that belongs to the dog living at your friend's house. I hope that all makes sense.