Apostrophes and plurals | The Apostrophe | Punctuation | Khan Academy

There is *one* extremely rare case in which we use apostrophes to make things plural. David and Paige, KA's resident grammarians, discuss this unusual case.

Watch the next lesson:

Punctuation on Khan Academy: Punctuation is the collection of squiggles, dots, and lines that we use to separate sentences and their parts. Is a question mark punctuation? Yes, and so is an exclamation point!

About Khan Academy: Khan Academy offers practice exercises, instructional videos, and a personalized learning dashboard that empower learners to study at their own pace in and outside of the classroom. We tackle math, science, computer programming, history, art history, economics, and more. Our math missions guide learners from kindergarten to calculus using state-of-the-art, adaptive technology that identifies strengths and learning gaps. We've also partnered with institutions like NASA, The Museum of Modern Art, The California Academy of Sciences, and MIT to offer specialized content.

For free. For everyone. Forever. #YouCanLearnAnything

[mendel]

Hi, I am still unclear why you did not add the apostrophe to CD's DVD's etc. How about SKU's does one need to add an apostrophe when the word is all upper cases and the added "s" in lower case to indicate plural? Thanks

After watching it again I think I got the gist of it.

If the word is lower case or a mix of lower and upper case, add the apostrophe before the s to make it plural.

If however the word is all caps such as CD DVD SKU etc then no apostrophe is needed before the s at the end.

In addition to that, single letters seem to need an apostrophe as in G's I's S's etc.

Thank you for your professional content and presentation and of course your humor and wit.

[MrJensenSucks]

I advise my students to use an apostrophe when pluralizing a single letter whether it's capitalized or not. Consider "I got four A's on my report card; A's are better than B's." When a sentence begins with the plural of the letter, it can be much more confusing: "As are better than Bs." Context helps, but As feels like a worm in my skull. Of course, an easy solution would be to simply rewrite the sentence so it's clearer, but "Pluralize with an apostrophe only when writing about letters" seems to be a simple enough rule, especially given the rarity of its occurrence. "Pluralize with an apostrophe when writing about lowercase letters but not capital letters" feels like an exception to an exception, which a student would forget by the time they got around to using the rule.
What's more, leaving it only to single letters also covers the likes of MP3s, DVDs, and the brain-itching SESs.

[frommarkham]

I think that apostrophes should be used to pluralize words which end in S so people won't think that it's misspelled.

[GR-lems]

Simple, you don't use lower case letters in the beginning, you use an uppercase letter.