A missing or misplaced apostrophe can be a source of irritation to the grammatically astute. But can you really spot an “incorrect” apostrophe? It’s not always so easy as being conscious of possessive forms of speech.
I like to use Farmer’s Market because it’s a frequently cited example.
We use apostrophes when the noun is possessive, so the apostrophe is correct here. Farmer’s is a possessive noun. Isn’t it?
There is another type of noun, not often thought of consciously by many people, that can be confused with possessive nouns. It’s called an attributive noun. Attributives look and act a lot like possessives but, instead of referencing ownership or possession, they simply indicate that there is an association–something is attributed to something else.
So do the farmers actually own the market? Or is it a market for farmers? Or a market of farmers? Or a market by farmers?
Are you still so sure about that apostrophe?
As usual, you will have to consult a few references. If you live in the US, Merriam-Webster is probably where you will want to look. They list farmers market as a nonpossessive noun: “A market at which local farmers sell their agricultural products directly to customers.”
Done. So the apostrophe is incorrect. Get rid of it, and the noun phrase is correct.
Not so fast. Notice that MW also lists the variants: farmers’ market and farmer’s market.
All three are correct? You just have to pick one?
Remember to consider which style guide you are using. AP (often used in the media) does not include the apostrophe for attributive nouns (also known as descriptive nouns). So if you randomly decided to include the apostrophe based on MW, you would not be following the advice of the AP stylebook, so you could be considered wrong if that’s what your document required. See this article for such an interpretation of punctuation rules (it’s a helpful article if you are following AP style). However, if you were supposed to defer to the Chicago Manual of Style, you would have to look for descriptive nouns under genitive case (see 5.20). CMOS keeps the apostrophe for descriptive nouns (the example they give is summer’s day–does summer own the day or does it describe the day?). Therefore, if you were following CMOS–but didn’t include the apostrophe–you could be incorrect unless the noun was definitely not a possessive (see this article for additional discussion on these points).
Unless the apostrophe is decisively possessive, it’s difficult to accuse a writer of being “wrong’ without knowing the style guide.