40 Spelling Rules – Suffixes

40 Spelling Rules - Suffixes



Hello, and welcome to the third mini-lesson on The 40 Rules of English, where we break down every beginner rule you need to know in English and ESL. We aren’t going to bog you down with a bunch of definitions today, because we have a lot of rules to cover! Just know that suffixes are the opposite of prefixes. While prefixes go at the beginning of the root word, suffixes go on the end to change the form of the root word. Let’s get specific!


  1. When a verb ends with a short vowel followed by a consonant (never w, x, y), double the last letter before adding “-ed” to make it past tense.

For now, we’re going to talk about -ed. It’s an important part of suffixes which turns verbs with short vowels + a consonant into past tense. In fact, it might be the most-used suffix out there! In our first suffix rule, we doubled the last letter (which, by the way, can never be w, x, or y) and then add -ed to make the word past tense. So, how would we turn this sentence into past tense? “I hug Mary.” We see the verb here is “hug”. It is a short vowel word, and has a consonant at the end that is neither w, x, nor y. Therefore, we double the last letter and add -ed! The sentence is now “I hugged Mary.”


  1. When the suffix “-full” is added to the end of a base word, one of the “l”s has to be dropped. This turns a verb into an adjective!

-full is a great suffix because of how easy it is to understand. It means “full of” or “possessing the qualities of” the root word. If something is “beautiful”, that means something is full of beauty. And if something is plentiful, that means it is full of plenty! Easy, right? One thing to note is that when you add -full, you have to drop one “l”. We’re not sure how or why the “l” gets chopped off, but don’t forget it!


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  1. “-ly” is added to turn some words into descriptors, or adverbs. If the word ends in a consonant, simply add -ly.

Another very common suffix is -ly, which turns words into adjectives and adverbs. Adverbs describe verbs. If you walk somewhere, an adverb would describe how you walk. Are you walking slowly? This rule follows a pretty simple pattern: if the root ends in a consonant, add -ly. That’s all! Lightly, smartly, quickly are all great examples.


  1. When adding “-ly” to words ending in “-ful”, it becomes -”fully”.

If we look back at rule 14, we see that the “l” is taken off of the suffix -full. However, this isn’t the case when we’re adding -ly. The suffix instead becomes -fully! Beautiful becomes beautifully, while plentiful becomes plentifully.


  1. When adding “-ly” to a word that ends in “-y” and have more than one syllable, change the “y” to an “i” before adding the “-ly”.

The syllable count in rule 17 is pretty important. Take the word “sly” for example. To make this an adverb, we’d just add -ly to make it “slyly”. For the word “heavy”, however, since it’s two syllables, we’d have to drop the -y for -ily. So instead of becoming “heavyly”, the word would be “heavily”!


  1. For most words ending in a consonant, add ‘-er’ or ‘-est’  to create the comparative and superlative forms.

The comparative and superlative forms are very important in English, and many other languages. They let you, for lack of a better phrase, compare nouns with other nouns. When words end in a consonant, just add -er or -est to make them comparative and superlative, respectively. For example, “She is smart” is a sentence where smart is the adjective. “She is smarter than him” would be an example of using the comparative. Who is she more intelligent than? Him. “She is the smartest” means she is above everyone in intelligence.


  1. When adding a vowel suffix to words ending in an -e, drop the e and add the suffix to create the comparative and superlative.

For rule 19, if the suffix starts with a, e, i, o, or u, and you’re adding the suffix to a word which ends in -e, then drop the -e and add -er or -est. Instead of writing “cuteer” or “cuteest”, you’d write “cuter” and “cutest”! Notice how we got rid of the unnecessary -e at the end of the root word.


  1. For words ending in a consonant + “y”: Before adding “-er” and “-est”, change the “y” to an “i”. This creates the comparative and superlative forms.

Here’s a pretty straightforward form we’ve seen before: the root word ending in consonant + -y. Just as before, drop the -y and change it to -i before adding -er and -est. A good example would be the word “hungry”. Notice how the word “hungry” ends in a consonant (“r”) + -y. So let’s apply rule 20. Drop the -y, and change it to an -i. Finally we’ll add -er or -est. The result? “Hungrier” and “hungriest”!


  1. Double the last letter before adding “-er” or “-est” to words that have a short vowel followed by a consonant. This creates the comparative and superlative forms.

We’re back to short vowels again. This time, the formula is short vowel + consonant at the end of the root word. If this is the case, then double the last letter and add -er and -est to make the comparative and superlative. A good example would be the word “hot”. We see this is a short vowel word followed by a consonant, so let’s double the last letter. That leaves us with “hott”. Now all that is left to do is add -er or -est. “Hotter” and “hottest”!



Wow, that was a lot of rules to cover! It only gets easier from here. 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 four: numbers. 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.