When to use apostrophe to show possession and when not to? [duplicate]

Question

Can you tell me what is the difference between these , and which one is correct:

girl problems.
girls' problems.

Microsoft products
Microsoft's products

Answer 1

They are all correct in their proper context, but they are not all examples of possession.

Prepositive Adjectives

The first example in each pair demonstrates the use of prepositive adjectives (a fancy way of saying, "an adjective that comes before the noun it modifies"). "Girl" is an adjective modifying "problems" and "Microsoft" is an adjective that modifies "products."

Specifically, "girl problems" is most often a colloquial phrase (as are all of its type) that suggest "problems with girls" or "problems specific to girls." A boyfriend who is suffering because of an argument with his girlfiend might respond to an associate that he is experiencing "girl problems."

The second example is more interesting because it involves trademark branding. Companies, brands, and trademarks often act like "people" in that they can possess things, but they also act as prepositive adjectives. It's a bit confusing because the word "Microsoft" is used as an adjective to modify "products" — but it is also a proper noun that circumstantially identifies the owner of the product. This is why there is some confusion. In this example, it really is a prepositive adjective and does not grammatically indicate possession.

Without all the modifying verbs, etc., possession always requires an apostrophe

You can always identify possession without using an apostrophe. For example, "the problems belong to the girls" or "the girls have problems." But when you don't use the connecting verbs you must use the apostrophe.

"Girls' problems" identifies problems that belong to a group of girls. It can be expressed, "the girls have problems" or "the girls are experiencing problems." Thus, a babysitter may explain to parents who have returned home that she didn't know how to handle the "girls' problems."

"Microsoft's products" identifies products owned by Microsoft.

It's worth noting

It's worth noting that company/brand/trademark names can throw substantial wrenches into the works. Technically, "Microsoft's products" describes products either owned or physically in the possession of Microsoft — not you. If a girl owns a copy of the Windows operating System, she possess that copy. "The girl's copy of a Microsoft product." Technically, even though Microsoft's user agreement probably says otherwise, it cannot be described as "Microsoft's product" because they neither own nor are in possession of the copy. On the other hand, if you were writing a review of Windows, you would legitimately describe it as "Microsoft's product" because you are discussing an item that is still owned and in the possession of Microsoft. E.G., "Windows 10 is Microsoft's latest product."

If your head gets to aching too much, let me know and I'll send you some of my aspirin. :-)