# Plural of numbers (as nouns)

I really tried to find an answer in Internet but turns out I've found two different answers for the same question: how do you say the plural of a number (used as noun)?

Let me elaborate:

Suppose I'm explaining to a child how to add (in Math). I'd say:

Four twos make an eight.

Or I could say:

Four two's make an eight.

On one webpage I found the first one to be correct. I asked to an online tutor about this and she told me the second one is correct. So, which one is correct? Is that a general rule? If the second one is correct, would that mean it applies to all numbers?

• It turns out that different people, and different cultures, express arithmetic calculations differently. "Four twos make an eight" is a reasonable thing to say when explaining multiplication of 4 times 2, but it's not the only way. As for plurals, treat the digits as nouns - ones, twos, threes, fours, fives, .... Ignore apostrophe plurals in dealing with arithmetic; in fact, avoid apostrophes whenever you can. Mar 14, 2019 at 22:30
• Most people educated in Britain would say that you were teaching multiplication rather than addition, unless you expected the child to proceed 2+2=4, +2=6, +2=8. Just being pedantic to pass the time. Mar 14, 2019 at 23:41

The first is correct:

Four twos make an eight.

It is good and right to say and write, "twos," in a situation like this, as with any number—following all the normal rules of adding "s" to make a noun plural... "fives", "twenties" (y -> i, +es), et cetera.

The apostrophe...

two's

...indicates a possessive, not a plural. That would be a different situation, such as if you were talking about the font the two was written in, "The two's serifs are larger in the Tex Gyre Schola font." Or, in Math, "The two's quotient can only be a one or a two if it is to be a whole number."

The reason you have found different answers is because this is a matter of style, not a rule, and different style guides will give different guidance.

For instance, here is what The Chicago Manual of Style (17th ed.), 6.116, says about the apostrophe:

The apostrophe has three main uses: to indicate the possessive case, to stand in for missing letters or numerals, and—in rare instances—to form the plural of certain expressions.

And in 7.15:

Capital letters used as words, numerals used as nouns, and abbreviations usually form the plural by adding s. To aid comprehension, lowercase letters form the plural with an apostrophe and an s (compare “two as in llama” with “two a’s in llama”).

the three Rs
x’s and y’s
the 1990s
IRAs
URLs

The Associated Press says the following about apostrophes beyond the simple posessive:

OMITTED LETTERS: I've, it's, don't, rock 'n' roll, 'tis the season to be jolly. He is a ne'er-do-well.
OMITTED FIGURES: The class of '62. The Spirit of '76. The '20s.
PLURALS OF A SINGLE LETTER: Mind your p's and q's. He learned the three R's and brought home a report card with four A's and two B's. The Oakland A's won the pennant.
DO NOT USE: For plurals of numerals or multiple-letter combinations.

Notice the conflicting guidance between the two when it comes to single capital letters.

However, according to both of these guides (which, together, are the most authoritative, in North America anyway), there would be no apostrophe for your number:

Four twos make an eight.

But you should follow whichever style guide you ascribe to.

Note, however, that this guidance has changed over time. About thirty years ago, it used to be that the apostrophe was used to make acronyms plural. We used to write DVD's, for example. That's something that most people no longer do.