40 Spelling Rules – Numbers

40 Spelling Rules - Numbers



Hello, and welcome to the fourth mini-lesson on The 40 Rules of English, where we break down every beginner rule you need to know in English and ESL. Numbers don’t really seem like they belong here in spelling rules, do they? Well, yes and no. It’s true, numbers don’t find their way into essays and articles often, but when they do, they can cause some confusion. There’s a standard that exists that tells us how to write out numbers (and when). So that will be our focus in this episode!


  1. When writing numbers less than ten, they should be written in word form not in digit form. Numbers greater than ten can be written in digit form.

Let’s start off with a pretty easy rule. Most of us should be able to count to ten (we hope). If you’re writing out any of these numbers, use words, not numbers! Anything above ten is OK to write in number form or word form. So we’re able to write eleven as eleven or 11. Got it? One, two, three, four, five, six, seven, eight, nine, ten must remain in word form. No exceptions! Well...that’s not entirely true. Remember, there are always exceptions to a rule. Let’s continue onto rule 23, shall we?


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  1. Always write a number in word form if it begins a sentence.

In the same way that a sentence must start with a capital letter, so too if a number starts a sentence, it must be written in word form. You can’t start a sentence by saying, “10 is my favorite number.” The correct way would be: “Ten is my favorite number.” This is true for all numbers, even those past ten. However, an exception here would be years, such as 2019.


  1. When ordinal numbers need to be included in a piece of writing, they are written in word form.

Don’t let the fancy language trick you. Ordinal numbers is just another way to say, “position in a series”. First, second, third. These numbers need to be written out. Yes, even if we’re talking about the four hundred fifty-third cookie.  

  1. For decades, spell them out in word form and use lowercase.

As a recap, a decade is every ten years. So if we asked you which decade was your favorite for music, and you wrote the 70s, we’d be very sad. Not because funk isn’t awesome, but because you need to write out 70s as “seventies”. A rule for a few of them is to add -ties to the root number to write the decade correctly: sixties, eighties, nineties.


  1. Always write decimals in number form with a 0 before the decimal point.

This sounds convoluted, but it’s just to avoid confusion. The number .5 looks a little to close 5, so we clear things up by adding 0. So, it should now read 0.5. Yes, a period still goes after 0.5, even though it looks a bit weird.


  1. When combining numbers, the first number is always written in word form.

Our last rule for numbers is easily the trickiest. Why? Well, this is all in the name of avoiding confusion, but it can still make your head spin if you mix the rule up. Let’s start with an example. The cat caught four 6 lb. mice. OK, easy enough. A cat was able to catch four mice. Each mouse was six pounds (which is, by the way, a disgustingly large mouse; if you have a mouse in your house that weighs six pounds, buy as many cats as you can).


Let’s rewrite this sentence incorrectly, to see why it might be confusing. The cat caught 4 six lb. mice. Well, it certainly looks weird. We might get confused about the quantity of mice in this sentence. Is it four mice or is it six, because we are supposed to write out numbers less than ten?


The cat caught four six lb. mice. While not technically wrong, this just makes it look, at first glance, like forty-six mice. The cat caught 4 6 lb. mice. While this sentence makes it looks like the cat caught a 46 lb. mouse. Someone call the record books. Or an exterminator.



Well done! As a recap, numbers often have to be written out, especially if they are below ten. Above all, remain clear when you write with numbers. If you reread a sentence, would you understand it as a stranger would?


Want to sharpen those skills and prove to yourself you have what it takes to master the first steps of English spelling? We’re proud of you (and we’re here to help)! That means you’re ready for mini-lesson five: ownership and apostrophes. If you aren’t quite ready, that’s OK! Use this lesson as a guide, and keep practicing every day. Practice builds the confidence you need to tackle even the most difficult of concepts. Check out our paths, decks, and other lessons today! See you next time.