Uh, mathworks.com, you must be kidding me.
I am not a grammarian, and although I teach English I do not know all the rules of grammar. I break a few, sometimes purposely and at other times without even knowing it. For the most part, I believe that if you've gotten your message across, mission accomplished. I also believe that people ought not to foist their idiosyncratic grammatical pet peeves on everyone. My mother--Hi, mom! I love you!--hates it when people say, "I'm standing on line" instead of "I'm standing in line," but there's nothing wrong with saying, "I'm standing on line." It's a regional thing, a colloquialism. It sounds wrong to my mom's ears because she learned to speak in a region where people stand in line.
Here's the thing: some grammatical errors get in the way of the clear communication of your message. Even if the readers of that facebook post or that sign or that email can parse out what you intended to say, s/he experiences a moment of confusion, and I would bet that you are trying to connect with rather than to confuse your reader. (If I'm wrong, carry on!)
I want to tackle the subject of plural (-es, -s) and possessive (apostrophe, apostrophe-s), and since it's a special day, I'm gonna get thematic:
"To all the fathers out there, Happy Father's Day!"
In that line, which you've probably encountered in some permutation many times today, we've got both plural (fathers) and possessive (Father's).
The plural is the easiest nut to crack. When you want to indicate more than one of something, tack on an "s" or an "es." Leave the apostrophe out of it. One father becomes two (or more) fathers. There are irregular plural nouns--for example, we say children not childs when we're talking about more than one of the little critters--but most nouns prefer a simple "s" or "es," and if you've grown up speaking English or a language related to English, you will intuitively know how to render a word plural.
Now here's where things get interesting. The rule about plurals? It applies to proper nouns too. You know what that means? Almost every sign announcing who lives in this or that house is wrong and, more importantly, confusing.
Let's say your last name is Jones, and you want to use the Dremel 1550 VersaTip to burn that badboy into a piece of pine and mount it onto a post in your front yard.
Go for it. Only don't write The Jones's or The Jones unless, like the Fonz, you go by the moniker the Jones. (Aaaaaaay.) If you are such a person, by all means burn your name as stated. But if your singular noun of a last name happens to end with "s," you need to make it plural by adding an "s" or "es" because, after all, not only one Jones lives in your house, but two or more Joneses live there. See how I wrote Joneses right there? That's the plural of Jones. That's what you want to carve into your sign if you want indicate the shared name of the people who live at your address.
If your last name doesn't end with "s" but a couple or three of you reside here, tack on an "s" or an "es," but remember to forget the apostrophe. Don't burn The Smith's into your plaque. Burn The Smiths into it. (Imagine it like this: The Smiths live here.)
But what if you want to add the word House to your sign? Now you need to go beyond signaling that more than one Jones lives here; you have to indicate that the house belongs to the Joneses. Put another way, the Joneses possess the house.
It's an established fact that in the world of dating it's inadvisable to be possessive. But in the world of writing, it's only a problem if you ought to be being plural or if you default to s-apostrophe. Disclaimer: the rules I am about to explain do not correspond with the rules followed by journalists. Those people dance to their own beat.
I had this crazy professor in my early years of graduate school--not in my Ph.D. program but at the place I got my Master's. That poor man. He was a wreck. Once he missed giving us our final exam because he lost track of time in the campus pub. But, boy, did he know his grammar. Here's a handy phrase he gave us:
Look to the left of the apostrophe.
Here's what it means:
- The Joneses' House: Joneses is to the left of the apostrophe. Joneses is a plural noun. More than one Jones must possess this house.
- The Jones's House: Jones is to the left of the apostrophe. Jones is a singular noun. "The Jones" must possess this house. Aaaaaaay.
- The Smiths' House: Smiths is to the left of the apostrophe. Smiths is a plural noun. More than one Smith must possess this house.
- The Smith's House: Smith is to the left of the apostrophe. Smith is a singular noun. The Smith lives here. I should ask him to make me some horseshoes.
Now I am going to blow your mind. See how, above, plural nouns like Joneses and Smiths take an apostrophe and singular nouns like Jones and Smith take an apostrophe-s to become possessive? The same rule applies if the singular noun ends in "s."
So if you wanted to observe that today is the birthday of your boss, you'd write, Today is my boss's birthday. Look to the left of the apostrophe. How many bosses? One.
If you had two bosses who shared the same birthday, you'd write, Today is my bosses' birthday. Look to the left of the apostrophe. How many bosses? Two.
I think that's about it. Go forth and make signs.