Increase your vocabulary FAST with Prefixes and Suffixes (Free PDF)

Increase your English vocabulary with the Root Word technique using prefixes and suffixes. I use this technique with my private students here in Japan. (And they love it!)

Increase English vocabulary with Prefixes and Suffixes

In this post, you will learn an easy way to increase your English vocabulary. We will add prefixes and suffixes to words we may already know to make new words. I call this the ROOT word technique.

Now there’s a video at the end of this post. Watch it to review and improve your English listening skills. AND a PDF worksheet download to practice this technique with new prefixes and suffixes.

This is also something I use to learn Japanese vocabulary. I’m sure it can help you understand and use English too.

Let me share a real story to explain how we can use the root word technique to easily understand more English words.

“What is a sweetener?”

~ I like to cook, and while I was looking at some new recipes, I saw a sweetener called “stevia” that was becoming common in North America. I did some research and I found that it has been used in Canada and America recently, but it has been used in Japan for more than 30 years! When I asked my students if they have heard about stevia we talked about sweeteners

Sweetener became the perfect word to introduce this technique because the word sweet is an easy and common word that everyone already understands.

Increase English vocabulary
Sweetener - two suffixes

Root word technique

A root word is the base (root) of a new word. When the root word is one that we already understand, it can help us learn the meaning of the new word. 

The root word of sweetener is sweet.

We know the meaning of the adjective sweet already, it describes a taste. 

“Sugar and honey are sweet.”

Oxford Advanced Learner’s Dictionary sweet [adjective]

Sweet can also be used as a noun (usually, a plural noun sweets) to mean candy. 

“My dentist said I eat too many sweets!” = I eat too much candy.

Oxford Advanced Learner’s Dictionary sweet [noun]

Sweeten is a verb that means: to make something sweet

“Many people use sugar to sweeten their coffee. Black coffee is too bitter for most people.”

(Bitter is the opposite of sweet, but we never use bitteren as a verb!)

Oxford Advanced Learner’s Dictionary sweeten [verb]

Increase your English vocabulary with the suffix -ER

So now we understand sweeten, how about our new word sweetener? Let’s look at some other verbs that have “er” added at the end and see what they mean.

In baseball, the person who throws (pitches) the ball is called the pitcher. The person who hits (bats) the ball is the batter and the one who catches the ball is…? 

That’s right! The catcher

A verb followed by -er is the name of the person or thing that does that verb. Increase English vocabulary

*And not only for people, the machine that dries our hair is a hair dryer, the machine that mixes (blends) our food and drinks is a blender.

A verb followed by -er describes the person or thing that does that verb.

Here are some more examples of nouns ending in -er.

A floor wiper wipes your floor.

Increase English vocabulary - wiper

A sharpener makes your pencils sharp. (It sharpens your pencils)

Increase English vocabulary. A sharpener makes your pencils sharp. (It sharpens your pencils)

A container contains (holds) something. Tupperware is a well-known company in North America that makes plastic containers.

What do you think a sweetener does? It makes things taste SWEET!

When we use the noun sweetener we are most often talking about one that has fewer calories than sugar. An artificial (not natural) sweetener. Please look at the infographic below for more examples of words made from the root word SWEET.

Sugar is sweet.

I like to sweeten my coffee with honey.

Do you have any non-calorie sweetener?

Oranges are sweeter than lemons.

Strawberries are the sweetest.

Too many sweets are bad for your teeth.

Increase your vocabulary
Root word practice with SWEET

Watch the video below to practice your English listening skills.

Increase English vocabulary with Prefixes and Suffixes – Advanced root word practice

Summer in Tokyo is very humid. I can make my apartment cooler by using the air conditioner.

[We can see now that an air conditioner is a machine that changes the condition of the air.]

Another machine that I like to use is called a dehumidifier.

A dehumidifier helps cool the air and I think it feels more comfortable than the air conditioner. Let’s use our root word practice on the word dehumidifier.

Increase English vocabulary 

Humid is an adjective that means – (of the air or climate) warm and slightly wet

“Summer in Tokyo is very humid.”

Humid is our root word. What about the other parts of the word?

There are 3 parts added to our root word.

We know what the suffix –ER means already. A verb followed by -er is the name of the person or thing that does that verb. What is the verb part of our word?

humidify [verb] to make dry air wetter (to add water to dry air)

Suffix -IFY

The suffix –IFY can mean “to make, cause to be” causing a word to become a verb.

To make something pure we can purify it. To make something clear we want to clarify something.

Winter in Tokyo is much cooler than the summer. A cold dry wind comes from the North, making the air dry. In the winter people in Tokyo may use a humidifier to make the air in their house or apartment more comfortable.

*Note that the suffix –IFY changes to –IFI when it is followed by the letter E.

A humidifier is a machine that adds moisture (water) to the air.

What about a dehumidifier? A dehumidifier is a humidifier with the prefix DE in front.

Prefix DE

The prefix DE is sometimes used to mean remove or separate.

In the winter airports have machines that spray warm water on airplanes to de-ice the wings. (Remove the ice from the wing of an airplane.)

Before you cook a fish, you should debone it. (Remove the bone.)

Can you guess what a dehumidifier does? It takes the water out of the air.

dehumidifier – noun – an electrical machine for removing water from the air

Tokyo weather is a common topic during my private lessons, so it’s a nice way to introduce the word dehumidifier and talk about root word practice to increase English vocabulary. Dehumidifier has a prefix and two suffixes so it’s perfect!


Use my Root word Technique to increase English vocabulary with Prefixes and Suffixes. Below are some other blog posts I have made that teach a prefix or a suffix.

How to use Over and Under as prefixes + Video (2020 update)
English suffix ~ish (Increase vocabulary + video!)
English suffix EN (Increase your vocabulary)
English suffix -PROOF Grow your vocabulary (2019)
English suffix ~ous Learn with lots of example sentences (Video)

Get a free PDF worksheet by clicking the image below.

Below is one of my first videos. I edited a small part out and uploaded it again in 2017 but it is still the original “quality” from 2013. It’s helpful and fun 🙂

7 thoughts on “Increase your vocabulary FAST with Prefixes and Suffixes (Free PDF)”

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