Confusing Suffixes -ize and -ify (How and When to Use Them)

One of my private English students asked me the difference between the suffixes -ize and -ify. Both are used to change existing words into new verbs that can mean – make or become. I did research and put together some examples with each suffix to help explain the difference.

The suffix-ize (one syllable) is generally used with root stems with more than one syllable. 
– a・pol・o・gize 
– mem・or・ize
The suffix –ify (two syllables) is more commonly used with root stems with one syllable.
– u・nify 
– pur・ify
There are exceptions! See the list below.

I put together some charts to show you how these prefixes are used to make verbs out of nouns and adjectives. This will make it easy to remember which words are used with the suffix -ify. Keep reading.

The Difference Between The Suffixes -ize And -ify

You can see that the usage of both of these suffixes can have the same meaning in the new verb that they make. 

-ize suffix (in verbs) ​to become, make or make like

popularize = to make popular

-ify suffix (in verbs) to make or become

purify = to make pure

Here is one difference between these two suffixes that you can use more as a guideline than as a general rule.

The suffix-ize is used with root stems with more than one syllable. Source

The stem of popularize is popular. popular + -ize = popularize
Popular has 3 syllables. pop・u・lar

The suffix -ify is more often (but not always) used with root stems with one syllable. 

The stem of purify is pure. pure + -ify = purify

*NOTE – The root stem is different than the root word. For example
The word specific has three syllables
But the root stem of the verb specify has only one syllable
The ‘C’ is added to the ‘I’ to form the second syllable. The last two syllables of the word come from the suffix -ify

As stated this is more of a guideline than a rule. I’ve compiled a list of common verbs with the suffix -ify and broken them into groups by the number of syllables. 

Every vocabulary word in this list has a link to its meaning.
Most of the links will take you to Oxford Learners which contains an audio link so that you can hear the correct pronunciation.
A natural example sentence follows each word so you can see how these words are used in English.

Verbs With The Suffix -ify

3-Syllable words with the suffix -ify
amplify I connected a heavy-duty battery to amplify the signal. 
beautify The city is spending some money to help beautify the park downtown. 
calcify As a baby grows and developes, several bones fuse together and calcify.
certify This document certifies that I have had all my vaccinations. 
clarify If you have any questions or you would like me to clarify any points from the speech please let me know.
classify At first, scientists weren’t sure how to classify the duck-billed platypus. It’s a mammal but it lays eggs. 
dignify I heard the stupid thing that he said but I don’t want to dignify it with a response.
falsify A good scientific theory is one that you can prove false. An idea or hypothesis that you can’t falsify is useless. 
fortify We boarded up the windows to fortify the house before the hurricane hits. 
gentrify Older neighborhoods in the downtown core are being gentrified to attract wealthier people to the area. 
glorify He’s a quality filmmaker but some believe his movies glorify violence. 
gratify We were gratified to work with such a big company. 
horrify Nigel has terrible eating habits. It would horrify most people to see what he eats in a day. 
identify We have identified the problem and come up with a solution that should be good for everyone. 
justify That’s a big expense, I’m not sure the company can justify that. 
liquify The dessert table was amazing! They liquify chocolate and send it through a fountain so you can dip your sweets in it. 
magnify The picture shows bacteria magnified 20 times its normal size. 
modify The carpenter had to modify the door to fit. It wasn’t the right size at first. 
mummify I learned how they mummified bodies in ancient Egypt. It’s kind of cool but it’s also a little bit gross. 
mystify We were all mystified by Brian’s behavior at the party. I think something must have happened to him before he arrived, he was acting very strange. 
purify The machine that purifies water is called a water purifier.
qualify I applied for a gold credit card but unfortunately, I didn’t qualify.
quantify The earthquake caused so much destruction, that it was hard to quantify the damage. 
rectify This is a serious problem so we need to rectify it quickly. 
signify In most martial arts a black belt signifies that the person has a lot of skill.
simplify I think we are making things too complicated. Let’s take a step back and simplify our approach.
specify When you book the hotel make sure you specify a non-smoking room. 
terrify Paul is terrified of cockroaches.  I don’t blame him, I hate them too. 
testify The president will testify before the committee tomorrow. 

*You will notice that many of the 4-syllable and 5-syllable verbs are made from 3-syllable verbs with a prefix added on. 

4-Syllable words with the suffix -ify
decalcify I have to decalcify my shower head every 6 months.
decertify In 2004, workers at the stores voted to decertify the union.
disqualify I was disqualified from the tournament after the first match. I argued with the referee too much.
electrify The farmer electrified the fence around his cows to stop them from running away. 
emulsify The oil in salad dressing can separate if you let it sit. It’s good to shake the bottle to emulsify the ingredients. 
humidify *This word is not used by itself very often. It’s most often heard inside other words like a humidifier or a dehumidifier.
objectify Lee-anne hates that magazine, she thinks it objectifies women. 
prequalify Based on my income and where I live pre-qualified for the mortgage. 
recertify My forklift license is out of date so I need to do the training again to recertify
reclassify After the truth came out his book was reclassified as fiction.
reunify I work for a nonprofit organization that works to reunify families split up by war. 
solidify When you pour maple syrup on the snow it solidifies and becomes like candy. 
4-Syllable words with the suffix -ify
declassify The government just released some declassified documents relating to the incident.
dehumidify *This word is not used by itself very often. It’s most often heard inside the word dehumidifier.

Watch this clip from my Root Word Video to see how we make the word dehumidifier.

resolidify Candle wax heats up, melts, and then runs down the side of the candle. It will resolidify as soon as it cools. 

Verbs With The Suffix -ize

Below is a small sample of verbs with the suffix -ize taken from my blog post How To Use The Suffix -ize (List, Definitions, 48 Examples).

apologize – to make an apology for doing something wrong

  • I apologize if anything I said was misunderstood. 

authorize – to give permission, to authorize

  • I don’t think that you are authorized to make those kinds of decisions. I’m going to call the boss and double-check. 

capitalize – to write or print a letter of the alphabet as a capital

  • You should capitalize the first letter of a sentence and any proper nouns. 

immunize – to protect a person or an animal from a disease, especially by giving them an injection of a vaccine [to make immune]

  • There is a debate now on whether or not we should immunize children under 4. 

jeopardize – to risk harming or destroying something/somebody [to make jeopardy]

  • Summerfield that immunizing young children may jeopardize their health.

legalize – to make legal

  • The country has voted to legalize marijuana so they can control and tax the sale of this substance. 

Thanks to Stony Brook University for this helpful resource and some details about these suffixes. SOURCE

This post is part of a group of posts that take a look at the suffix -ize. Visit these other posts and do a deeper dive into this suffix.

How To Use The Suffix -ize (List, Definitions, 48 Examples)

What Is The Origin of The Suffix -ize? (History and Development)

What’s the Difference Between the Suffixes -IZE and -ISE?

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