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The Floss Rule for Spelling

Have you ever wondered why some words have a double consonant at the end (such as sniff), while other words do not (such as dog and bat)?

The answer is easy–and we call it The Floss Rule. It’s a really simple spelling rule that helps kids remember when to use a double consonant at the end of a word.

Check out this handy rule in the video below, and then read on for free printable spelling rule posters and a sample lesson!

Why Do We Call It “The Floss Rule”?

The rule states that if a word has only one vowel and ends in F, L, or S, double the last letter.

The word floss is a perfect example of this rule, and it also contains the letters f, l, and s! That makes “The Floss Rule” a pretty handy name, doesn’t it?

infographic showing the floss rule for spelling

More tips and tricks like this one are taught throughout the All About Spelling program. Want to see more? Download these two free resources to see just how easy teaching spelling rules can be.

Download All About Spelling Level 1, Lesson 17.
This lesson shows how we teach doubling a consonant at the end of one-syllable words.

pdf-icon-transparent-background2-small-p3

Download our free Spelling Rules Posters.
This handy resource will help make learning three important spelling rules easy and fun to remember for your children.

Has the Floss Rule helped your child? I would love to hear about it in the comments below! And check out our other spelling rules, too!

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Pal

says:

Pal, pas, has, gas, etc. Let’s make it a game. How many words can you find that that violate this rule?

Robin

says: Customer Service

All About Reading and All About Spelling teach rules that are reliable 95+% of the time, and the Floss Rule certainly meets that criteria. Yes, there are exceptions, and some are very common words (if and yes come to my mind), but there are approximately 500 words that follow the rule and only approximately 20 that break it, for about 96% reliability rate. This rule allows children to successfully spell so many words, and requires them to learn just a few as exceptions.

By the way, I’m inclined to argue against gas and pas. Gas is an clipping of gasoline, a shortening of the word, jargon. It has come into common usage but retains it’s spelling from the longer word. (The same happened with bus from the word omnibus. Although, gas and bus are counted among the approximately 20 exceptions.) Pas is simply not an English word, so English rules do not apply.

Georgia Jeffery

says:

Hi, I am a learning support teacher with many students who have spelling and reading dificulties. Thankyou for your great information and knowledge to help support struggling students.

Robin

says: Customer Service

You are so welcome, Georgia, and thank you for the work you do for your students!

J. C.

says:

So, in addition to all the information already given:
Calligraphy is hobby of mine, and I can at least throw out a theory.
Although the exact reason isn’t known for some of these occurrences, it is very likely that it comes from early scribes. During certain periods of history, astheics took precidence over legibility or practicality. So it is entirely possible that a group of scribes decided that some words looked better with the double letters at the end. “tall” is more pleasing to the eye than “tal.” The records for why these decisions were made or who made them are practically non existent though. At best, we can look at documents and see when they became standard practice. But they didn’t usually record (or at least preserve the record) why they did what they did.

Robin

says: Customer Service

What an interesting perspective, J.C. Thank you! I can very much see how double L could have been for aesthetics.

Meghan

says:

I am doing level one with my daughter, and she wants to know WHY the floss rule exists. Why aren’t all of these words just spelled with one f, s or l instead of two? I have tried to Google the answer but haven’t found anything. Can you enlighten us? Thank you!

Robin

says: Customer Service

Meghan,
I love that your daughter is really thinking of the why of things! I did some digging, and found a few things.

First, the doubling of these letters did not start as a rule. Rather, the rule was applied centuries later when the spellings were already established, when people noticed this pattern already existed. Put another way, people didn’t decide to have this rule and started doubling these letters. Rather, they were doubling these letters for hundreds of years before this rule was put into words. It was something English writers were doing intuitively even before spelling was standardized.

It seems that the practice for doubling these particular letters came about separately for each letter. It is thought that S was doubled to show that it was not a plural -S suffix being added so that class is not more than one cla as it would look like if we spelled it clas.

For F, way back in history, lowercase f and certain s letters looked REALLY similar. Specifically, English had a “long s” and a “round s” and had rules for when each was used (this was used in both handwriting and for a couple of centuries after the printing press became commonplace). Well, the long s was hard to distinguish from lowercase f, so it is thought that doubling f at the end of words was to make the f clearer. (By the way, this reasoning for double f is less agreed upon than the reasoning for double s, but I could find no other reason for double f.) Anyway, here is a Wikipedia article on Long S that includes examples of what the letter looked like, including the original US Bill of Rights that used the long s in the word Congress right on top, so it looks like Congrefs to modern eyes!

The best I could find for double L was, “Most final doublings of this kind serve a specific purchase. There does not seem to be such a justification for -LL, however.” So, apparently, even scholars of historic English can’t find a reason for doubling L, but it is done with such regularity that it is a very reliable rule.

By the way, the resource book The ABC’s and All Their Tricks by Margaret M. Bishop was very helpful for this question, as well as many others about English spelling.

I hope this helps alleviate your daughter’s curiosity some! Great question! I love digging into such things.

Meghan

says:

THANK YOU so much!! I am going to share this with her. She is always asking me about the whys of English spelling and I can never answer her beyond saying that English has been influenced by a lot of other languages, because that’s all that my Googling has turned up. She HATES it that there are so many exceptions to various spelling rules. I shared what you wrote in an earlier comment, about the reasons behind the exceptions to the floss rule, and that was really helpful for her. I am going to see if my library has that book you recommended ☺️.

Robin

says: Customer Service

You’re welcome, Meghan!

If you can’t find The ABCs and All Their Tricks at your library, see if you can pick it up used. I find it to be a helpful reference book.

And, if your daughter has more questions, just ask! We’re happy to answer the best we can, and at least I enjoy such questions (I’m pretty sure my coworkers do too)! You can ask here, or email us at support@allaboutlearningpress.com.

Ami Shah

says:

This a very helpful to the children. please send me e newsletter for great tips on reading and spelling.

Robin

says: Customer Service

I’m glad this is helpful, Ami! I have signed you up for the newsletter, and you should have received the welcome email by now. Let me know if I can help you with anything else.

Sadiq Muhammad

says:

This a very helpful to the children. please send me e newsletter for great tips on reading and spelling.

Robin

says: Customer Service

Sadiq,
I have signed you up for our email newsletter and you should receive the first welcome email shortly.

Elizabeth Ramirez

says:

My grandson needs to understand the rules of brushing his teeth. This will be very informative.

Poornima Ramesh

says:

Send me the weekly e-newsletter for great tips on reading and spelling.

Robin

says: Customer Service

Poornima,
I have signed you up for our email newsletter. You should have received the welcome email by now. Let me know if I can help you with anything else.

David Mckenry

says:

Very interesting and informative, thank you.

Robin

says: Customer Service

You’re welcome, David. Thank you.

Holli

says:

I love the use of FLOSS to help remember the rule. It’s brilliant! My daughter has asked about the exceptions you listed and wants to know why those words don’t have the “s” doubled? The words all follow the requirements for the rule but we don’t double the ending letter. Could you help explain why? Thanks.

Robin

says: Customer Service

Holli,
Your daughter is really thinking about words, and that is great! That kind of thinking means deeper learning is happening!

Well, gas and bus are exceptions because they are abbreviations. They are short for gasoline and autobus (I was surprised to learn that bus was an abbreviation of a word I had never heard of before!).

Chef is an exception because it is a French loan word. Words from other languages don’t have to follow English rules.

Plus was brought into English without change from Latin (it is spelled, pronounced, and more or less means the same). So, for a long time, it was like putting “et cetera” within an English sentence. It was Latin and the Latin spelling remained. However, it’s been in English for so long that it really ought to have had it’s spelling changed but that never happened. So, plus is spelled with one S because it was always spelled with one S. Sigh.

Gal is, and has always been, slang. It arrived from a strong regional accent version of the word girl, and along the way it started to be written the way it was pronounced (such as “because” sometimes written as “becuz”). Still, it probably should have been spelled in accordance to English rules but never was.

If, yes, this, and us are spelled the way they are because very common function words in English are spelled with as few letters as possible.

English is known for having exceptions to its rules, so please let your daughter know that there will always be some words that be rule-breakers. It’s just how English works. Sigh. However, All About Reading and All About Spelling focus only on the rules that are the most reliable and have the fewest exceptions. If a rule is reliable only 75% of the time, we don’t teach it!

Considering how few words in English are exceptions to the Floss Rule and how many words do follow it, it is highly reliable. Hundreds of words follow this rule and it reliable about 97% of the time!

Meagan Marazzo

says:

Love this!

D.Sammy

says:

Thanks for these tips
Just like to know how and when double consonant in the middle(lesson,spelling,middle)

Robin E.

says: Customer Service

The reason a consonant in a middle of a word may be doubled is to protect the short vowel sound. This has to do with open and closed syllables. Please look over our How to Teach Open and Closed Syllables blog post for an overview of them.

When there is only one consonant between two vowels in a two-syllable word, such as the word robot, the word is usually divided so the consonant goes with the second vowel, making the first syllable an open syllable. So, robot is divided ro-bot. Vowels say their long sounds when in open syllables, so robot sounds like it does.

But sometimes we want a word to have a short vowel in the first syllable even though it only has one consonant sound between the vowels. If we tried to spell the word rabbit with only one B, it would result in the A saying the long A sound, and the word wouldn’t be correct. So, the B is doubled so that the word is divided rab-bit, with the first vowel in a closed syllable saying its short vowel sound.

There are exceptions to this, where there are words with short vowels in the first syllable but only one consonant between the vowels. Examples are cabin, habit, and topic. However, the majority of words will double the consonant to protect the short vowel sound.

I hope this helps you understand, but let me know if you have additional questions. I’m happy to help!

Josefina H.

says:

Thank you for sharing with us.

Robin E.

says: Customer Service

You’re welcome, Josefina!

Deanna

says:

These tips and tricks make spelling so much easier!

Robin E.

says: Customer Service

Thanks, Deanna!

Deanna

says:

How did i never know this? Thank you for these tips and tricks!

Robin E.

says: Customer Service

You’re welcome, Deanna! I think many have not heard of the Floss Rule.

Ginny

says:

Definitely printing out the poster! Thank you!

Robin E.

says: Customer Service

You’re welcome, Ginny!

Jessica

says:

We’re just now getting to this and I’m amazed at how well my son can already spell and read! This is such a great program…I’ve even learned a thing or two from this :)

Robin E.

says: Customer Service

Glad to hear it is going so well for you and your son, Jessica! Keep up the great work!

Angela

says:

This rule has been so helpful for my son AND me! Thanks for making spelling fun!

Robin E.

says: Customer Service

You’re welcome, Angela! Glad to know this rule is helpful.

Dawn

says:

What a great way to remember this rule and such a helpful poster! Thank-You!

Robin E.

says: Customer Service

You’re welcome, Dawn!

Amanda Dunville

says:

I love this! This is the level of spelling my son is at and what an easy rule to explain to him to help him succeed.

Rebecca Baertlein

says:

I knew this rule but never noticed this fun way to remember it!

Robin E.

says: Customer Service

Rebecca,
It is helpful to make rules easy to remember!

Brandy

says:

Thank you for sharing such good tips and rules

Robin E.

says: Customer Service

You are so welcome, Brandy!

YaadStyle Homeschooling

says:

Great explanation. Thank you for the poster as well. Great video. Thank you so much.

Robin E.

says: Customer Service

You’re welcome!

Cassie

says:

Good to know!

Bobbie-Jo Saylor

says:

The Floss Rule has been great for my 2nd Grader! We printed off the posters and it has really helped!

Robin E.

says: Customer Service

I’m so glad to hear that the posters were helpful, Bobbie-Jo!

Kristin Tucker

says:

This is really helpful! Thank you. 🥰

Lynn

says:

Key words are a great way for children to remember spelling rules!

Candy

says:

What a great concept! All About Learning is great!

Robin E.

says: Customer Service

Awww, thank you, Candy!

Jenny Beth Penrod

says:

The little extras are what make All About Learning great!

Beth

says:

I love these fun posters! All About Reading has been the key to success for my dyslexic son. I’m excited to start All About Spelling with him soon!

Robin E.

says: Customer Service

It’s great that All About Reading is working well for your son, Beth!

Lori Mahan

says:

I have never heard of the floss rule. Love it. I need the spelling to help cloase the gaps. Wish I could get my school to purchase this to help us. Main stream publishers don’t do enough spelling, grammar, or writing.