I typically don’t use an apostrophe with plurals in any situation, but I always assumed that the use of an apostrophe in constructions like acronyms:
Forty BA’s were given out to students this year.
or numbers:
Though the greatest period instability occurred during the 1950’s when. . . .
was more or less ok. I would personally use BAs and 1950s here, but I've never thought the apostrophe in this case was necessarily “incorrect”. What say ye?
My answer focuses on the header question about decades—which is the question that most readers will probably expect to find answers to here. With regard to decades expressed in numerals rather than spelled out in letters, some style guides recommend omitting an apostrophe, while others recommend including it. For example, from The Chicago Manual of Style, fifteenth edition (2003):
9.37 Decades. Decades are either spelled out (as long as the century is clear) and lowercased or expressed in numerals. No apostrophe appears between the year and the s.
the nineties
the 1980s and 1990s (or, less formally, the 1980s and '90s)
The Associated Press Stylebook (2002) adopts a rule very similar to Chicago's:
decades Use Arabic figures to indicate decades of history. Use an apostrophe to indicate numerals that are left out; show plural by adding the letter s: the 1890s, the '90s, the Gay '90s, the 1920s, the mid-1930s.
The Oxford Guide to Style (2002), while differing with Chicago and AP on capitalizing the spelled-out decade name (Oxford University Press prefers this) and on using abbreviations like '60s (OUP condemns this), agrees with Chicago that the plural numeral form should be spelled without an apostrophe before the s:
To denote simple ten-year spans OUP style prefers, for example, 1920s or 1960s to nineteen-twenties or nineteen-sixties. To denote decades of a specific character (say, the Roaring Twenties, the Swinging Sixties) OUP prefers Twenties or Sixties to '20s or '60s.
But Words into Type, third edition (1974) takes the opposing view:
In referring to decades, the sixties or the 1960's is generally preferred (not '60's, '60s, 60's, or 60s; the last form is used occasionally for ages of persons).
The New York Times Manual of Style and Usage (1999) agrees with Words into Type about the apostrophe, although about little else:
decades should usually be given in numerals: the 1990's; the mid-1970's; the 90's. But when a decade begins a sentence it must be spelled out. [example omitted]; often that is reason enough to recast the sentence.
Clearly the question of how to render a particular decade in print is a style issue on which reasonable style guides may differ. Follow the one you have to follow, or choose the one you like.
Not an easy question. With dates, the rule is simple: no apostrophes. It's "1960s" and so forth.
The apostrophe is needed when it serves to avoid confusion: She earned all A's and B's.
The style sheet I received when I was working on texts for publishers suggested 1920s, but did not claim that 1920's was incorrect. Writers need to be aware that all magazines, newspapers, and publishers have their own style sheet for many of these questions and that there is no unanimity among them. BTW, the answer above that 20's is correct because the apostrophe indicates something missing as in a contraction is incorrect. One of the reasons apostrophe use is so confusing is because using 's to indicate the plural form of things like decades, or grades on report cards has always been acceptable. It is this rule that confuses writers who then incorrectly use the 's for plurals such as apple's and other nouns such as family names (the Smith's). It is to avoid this error that style sheets recommend the lower case s as the plural for I received 4 Bs on my report card, but if I am an A student, it is context that explains that As stands for grades not the comparison.
Best solution in such situations--find an alternative. Write the Roaring Twenties.
I think when referring to the entire group of years that make up an entire decade (and thus indicating plurality), the proper form is 1920s without the apostrophe because you are essentially stating the following: "all the years that make up the decade which begins with the year 1920" when you use this construction.
When trying to indicate that something belongs to a particular decade, you may use the apostrophe to indicate possession. For example, the apostrophe in the phrase "1920's music" would imply that you are referring to music that was composed, published, recorded, or popular during the decade which begins with the year 1920. In this case, the music belongs to the decade.
As others have said previously, the apostrophe is a way to indicate that something in a word is missing. In one case, it may indicate the omission of numbers (ex. '20 instead of 1920). In another case, it indicates the omission of words which may be used to expression possession (ex. 1920's music instead of "music that was recorded in the decade that began with the year 1920). It is never, never, never used to express plurality.
This has puzzled me forever but only because of the incredibly variant information regarding what's acceptable. Prior to that, I didn't think I had an issue with how to address it. I am no master of English by any means but English and its variants have always fascinated me, especially once I started coding.
I learned that a single apostrophe (') is predominantly used in English words for these reasons:
If that remains true, then it is an easy thing to address regarding decades in American English:
A. If the decade is pluralized, no apostrophe. B. If "[pluralized decade]" possesses the following subject, use an apostrophe AFTER the "s".
e.g.
"Our kids were raised in the 70s." OR "Our kids are part of the 70s'(s) generation"
This is the same as any other situation in American English when a group is expressed as a plural and whether or not it is possessive in the sentence:
"When we camp, we can stay at one of many KOAs." "KOAs'(s) multiple campgrounds meet our needs when we travel."
OR
"There are several dojos near my house for Tai Kwan Do." "The area dojo'(s) tournament is open to all belt-holding competitors."
OR, a more classical example:
"The Jones family moved next door." "That's the Jones'(s) Tesla." "We refuse to let the Joneses tell us how to live."
Again, not saying I'm correct but that's my understanding that's saved confusion.
Based on the rule of word contraction, like in "aren't", the apostrophe replaces one or more subtracted letters, which means the decades can be expressed as "the 1920s" or "the '20s", meaning that the apostrophe is used to show the subtraction of the "19" prefix.
If a child left a note on the kitchen table to tell his mother about his report which is more clear: Mom, I made all a's on my report card. Mom, I made all as on my report card.
This proves for clarity, you need to use 's to form a plural in rare cases. I learned the expression is "I am learning my ABC's and 123's in kindergarten." Mind your p's and q's means mind your pints and quarts which came from the Gold Rush days in saloons where bartenders kept a chalkboard tabulation of the pints and quarts ordered by customers, so they could pay up later. They would say “Mind your p's and q's” so people would reference the board and control their spending on liquor.
The grammar rule for using 's when expressing 123's, ABC's, A's, B's, C's, 1920's, 1940's, 1960's, 1980's and so on has existed for centuries.
Now, it seems to depend on which style guide you are using. Words into Type, third edition (1974) takes this view: In referring to decades, the sixties or the 1960's is generally preferred (not '60's, '60s, 60's, or 60s; the last form is used occasionally for ages of persons). The New York Times Manual of Style and Usage (1999) agrees with Words into Type about the apostrophe, although about little else: decades should usually be given in numerals: the 1990's; the mid-1970's; the 90's. But when a decade begins a sentence it must be spelled out; often that is reason enough to recast the sentence.
For centuries, 's has been used to indicate some plurals in rare cases. Shakespeare wrote: “By my life this is my Ladies hand: these bee her very C’s, her V’s, and her T’s, and thus makes she her great P’s. It is in contempt of question her hand” (Twelfth Night, act 2, scene 5 [1st folio, 1623]; and note the absence of an apostrophe, and the plural ending, in the possessive “Ladies”).
In its first eleven editions, CMOS advised writing “the three R’s,” after which it became “the three Rs.” But the intent of the rule has remained the same: use an apostrophe wherever it is needed to prevent a misreading. And as anyone who got A’s in chemistry (or knows their Agatha Christie) might tell you, sometimes an apostrophe can spell the difference between a letter grade and a poison.”
Consider that many grammar school age children are still being taught the way people were taught in the 1800's. There are still new books instructing this way. Take note of the titles of these books for elementary grades: “ABC's And 123's: Writing Practice Workbook” by author, D. C. Kail in paperback released on September 2, 2017, and it is available on Amazon. “The ABC's and All Their Tricks: The Complete Reference Book of Phonics and Spelling” by author, Margaret M. Bishop. These exist for pre-schoolers: a book and a video from 1998 called “Blue's Clues ABC's and 123's.”
If this rule was good enough for Shakespeare, I don't see why the CMOS and other style guides have changed it. Many known style guides have NOT changed the centuries old rule.
