The -ious suffix

All of those vowels and two different pronunciations make this a tricky suffix


Hi again, and welcome back to Seattle Learning Academy's American English pronunciation podcast. My name is Mandy, and this is our 147th episode.

To read the transcripts and to find links to free lessons associated with this episode, go to and click Episode 147. Pronuncian is spelled p-r-o-n-u-n-c-i-a-n.

I notice that a lot of my students have trouble with words that end in the -ious suffix, as in the words cautious and previous. If you've never had the -ious suffix explained to you, seeing the vowels i, o, and u all together can cause a little confusion. I mean really, how many vowel sounds are in that suffix?

Remember we can count the number of vowel sounds by counting syllables. The word cautious c-a-u-t-i-o-u-s, has only two syllables total: one on the word's stem, and one on the suffix cau-tious. The word previous p-r-e-v-i-o-u-s, has three syllables: one on the stem, and two on the suffix pre-vi-ous. Lucky for us, there is a pattern to help us understand what's happening here.

The -ious suffix is a little extra difficult because it's the letter before the suffix that dictates how the suffix itself is pronounced.

Let's start with t+ious and c+ious. Both of these combinations are pronounced as shus. The initial consonant sound, whether it's a t or a c is pronounced as an sh sound. Then, the vowel sound can be thought of as either schwa or the short u. Dictionaries mostly transcribe the sound as schwa, which essentially is a very quick short u (short u). Finally, the last consonant of the suffix is an s sound, just as we'd expect. So we get shus.

Examples of t+ious and c+ious are the words cautious, nutritious, precious, and delicious. The error I hear students make is trying to add a small y sound into the suffix. I know, it just doesn't seem possible that the i-o-u combination of vowel letters can be pronounced as just schwa, but it is. The word cautious is pronounced as cautious not as caut-y-ious. Yes, the difference is small, but it is noticeable by native English speakers. I'm going to say those example words again, and give you time to repeat after me:


Not to confuse you, but I'd like to quickly add that there are also two common x+ious words with the same pronunciation of shus. Those are the words anxious and obnoxious.

Unless there is a t, c or x before the -ious suffix, the suffix is pronounced as i-ous, with two vowel sounds: first the long e, then schwa. Going back to our initial example word, we have previous, pre-vi-ous.

Some other common words with the two-vowel suffix pronunciation include:


It is important to be ready for both of these patterns because there are around the same number of English words for each pronunciation of the suffix. This is because the consonant before the -ious is the letter t or c more often than the other letters. I encourage and learners of English, and teachers of English, to focus a little more on getting the shus pronunciation of t+ious and c+ious correct because it's less intuitive, even if it is just as common as the i-ous pronunciation of the word previous.

Now let's practice. Here are eight words that are pronounced shus:


And here are eight words pronounced i-ious:


It was this odd shus pronunciation of the t+ious and c+ious suffixes that made me want to add suffix pronunciation information to the new lessons and the new, second edition of Pronunciation Pages. I'll link to the sh sound lesson from this episode's transcripts for you to see what I'm talking about. You can click the Products link on to find information about buying Pronunciation Pages, either as a downloadable ebook or as a physical book that we can ship to you.

Don't forget, you can let us know what you'd like to learn about by posting on our Facebook wall! Just go to We'll also post there when new content has been added to any of our websites.

That's all for today. This has been a Seattle Learning Academy digital publication. SLA is where the world comes to learn.

Thanks for listening.


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About the ESL/ELL Teacher

Mandy has been teaching ESL, pronunciation and accent reduction since 2005 at Seattle Learning Academy, an English language school in Seattle, Washington, USA. She uses her experience with intermediate to advanced students to create the topics that most affect students living and working in the United States and can help them communicate better and more clearly.

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