Errors abound when pluralizing terms. This video (about 15 seconds in) puts an apostrophe on the end of “mom” i.e, “mom’s,” intended for the plural of “mom”, which is “moms”.
That kind of error makes me disregard the true message of the video. Like most people, I hold public documents to a higher standard than informal writing.
Recently I bought a skin care product that had the word “ethnicity’s” in the text, when the plural “ethnicities” was intended.
Here’s the Merriam-Webster’s definition of apostrophe:
Main Entry: 2apostrophe Pronunciation Guide
Inflected Form(s): -s
Etymology: Middle French & Late Latin; Middle French apostrophe, from Late Latin apostrophus, from Greek apostrophos, from apostrophos turned away, from apostrephein to turn away, from apo- + strephein to turn — more at STROPHE
: the mark ‘ or ‘ used to indicate omission of one or more letters or figures (as in can’t for cannot, judg’d for judged, wish’d for wished, mascara’d for mascaraed, ’76 for 1776), to mark the possessive case of English nouns and of certain English pronouns (as in Bill’s, Moses’, women’s, boys’, anyone’s) or the plural of letters (as in two a’s) or of figures (as in three 7’s) and sometimes of words that are not normally nouns (as in no if’s or but’s),
to set off an inflectional or derivational suffix from a word that is
pronounced by uttering the name of each of its letters (as in their IQ’s, he OK’s it, GOP’er), or to constitute a terminal quotation mark
The confusion lies in the use of an “‘s” to make a noun plural. The nouns that are made plural with the addition of an apostrophe plus an “s” are rare and usually colloquial. Numbers are commonly written with the “‘s” (we’ve all seen the year terms written this way e.g. The 1980’s), and as the entry above states, initialized words like RSVP’s and AM’s or PM’s.
The trick to this is to notice usage and commonality. We’ve all heard the term “moms” in conversation if not so often in print. It’s safe to construct the plural in the traditional manner. With the initialized words, contructing the plural with an apostrophe makes it easier to read because we are accustomed to seeing the singular in print, e.g. OK and OK’s – OKs looks strange and may trip up a person reading aloud or silently, even within context.
When in doubt, use the regular construction of adding an “s” or “es” to words when writing a plural noun. If the word is an initial or a number, or if it just plain looks weird with a plain “s,” then use an apostrophe. The grammarians can figure out the rest.