How Many English Words are Not Decodable?

Edward Wong The Educational Parenting Blog Leave a Comment

Although many people believe that the English language is full of words that don’t follow spelling rules, few words are truly undecodable.

People often think that the English language is difficult for kids to learn because it has so many irregular spellings that don’t look the way they sound. It is true that some English words have irregular spellings—take the first word in this post, for instance. The word “people” is spelled according to an old pronunciation, even though we pronounce the word more like “peeple” today. But the truth is that these words are rare exceptions, and the overwhelming majority of words we encounter every day are perfectly possible to decode (that is, “sound out”) based on how they are spelled.

“Hold on!” you might be thinking, “I can think of plenty of examples of weird, everyday words. How are you supposed to sound out a word like knight?”

That’s a great question!

The answer is that “knight” actually follows common English spelling patterns. The “n” pronunciation for “kn” spellings is found in plenty of familiar English words, such as “know,” “knee,” and “knife.” Likewise, the “long-i” pronunciation of “igh” is found in the words “sight,” “right,” “might,” and “flight.” These ordinary words will already be part of the oral vocabulary of children learning to read.

Children are perfectly capable of recognizing and applying the patterns discussed above, so long as we teach them that more than one spelling pattern can make the same sound, as in the words “no” and “know” or “right” and “rite”.

Conversely, we also must remember to teach them that the same letters can make different sounds when used in different combinations. For instance, although “gh” combined with “i” makes the “long-i” sound in the examples previously discussed, it can also make the “f” sound when combined with “ou” (as in “cough” and “enough”).

There are far too many examples like these to discuss them all here, but the point is that these spellings are all, in fact, decodable. So how many English words, exactly, are not decodable?

The answer to that question is not exactly clear, but linguists and researchers have studied the problem. Many educators [i] point to a 1966 study [ii] by Stanford professor of education Paul R. Hanna which suggested that only 16%, but possibly as little as 4%, of words in English are not possible to sound out and must be memorized. More recent studies [iii] have suggested that Hanna’s research may have failed to take into account vowel complexity, but have not been able to propose an updated or more specific proportion of undecodable words than the original study.

Whatever the true number of undecodable words is, the evidence suggests that it is much smaller than the number of supposedly “undecodable” words that kids are being taught to memorize in the classroom.

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[i] Moats, Louisa C. “How spelling supports reading.” American Educator 6.12-22 (2005): 42.

[ii] Hanna, Paul R. “Phoneme-grapheme correspondences as cues to spelling improvement.” (1966).

[iii] Kessler, Brett, and Rebecca Treiman. “Relationships between sounds and letters in English monosyllables.” Journal of memory and Language 44.4 (2001): 592-617.

About the Author

Edward Wong

Edward Wong is a primary tutor and the Senior Designer at English Cosmos. He teaches children how to read, coaches parents on education in the home, and has been passionate about reading education since 2019. He graduated from the University of British Columbia with a Juris Doctor degree and qualified as a Chartered Professional Accountant (CPA).

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