I think teaching word parts (roots, suffixes, and prefixes) is overrated.
Yeah, I said it.
I had a great example in class recently. The word harness came up in a listening, as in harnessing the power of information. One of my advanced ESL students gamely tried to analyze it as har + ness.* And of course got nowhere. In my next class, we used the word sufficient and I was trying to figure out why it didn’t follow the pattern of stressing the syllable before the suffix -ic (Pacific, specific, electric) until I quickly realized that of course the suffix is -ent, and the “ic” is part of the root word (suffice, from the French and Latin, etc. etc.).
To be clear, I’m not saying that no word parts are worth teaching. The frequent and productive affixes (prefixes and suffixes) are very useful (e.g., co-, re-, inter-; negative prefixes; and the numerical prefixes like uni-, bi-, tri-, mill-, etc.). And obviously we need inflectional suffixes (grammatical bits like -s, -ed, -ing). It’s also definitely worth spending time on the most common derivational suffixes, which change words from one part of speech to another (-ous, -ment, -ly,-ize/-ise, etc.), but not as a standalone skill (here’s a good list with the most common affixes marked). For example, it’s really important for academic readers and writers to understand and use nominalization effectively as academic and scientific writing draws heavily on grammatical metaphor (see Units 5 and 8 of Grammar Choices), but this could be taught in the context of summary writing, rather than a lesson specifically on suffixes. Likewise, there is some benefit to teaching words as families, providing all family members are frequent enough to merit attention (economics, economist, economic, economical, economy). I would steer clear of very low frequency forms, though (e.g. vary, variation, variety and variable but probably not variability and variance except for statistics majors and quantitative researchers).
In general, I’m much more skeptical about teaching roots or stems.
The first problem is textbook exercises that can really only find one useful example and have to stretch to low-frequency words to find other examples of words derived from the same root. After you’ve figured out the circumference of a circle, you end up introducing circumlocution or circumnavigate just to fill out the exercise, which very few students will ever need or, if they do, will learn in context some other time. I suppose it’s nice to know that -cide means kill, but once you’ve figured out suicide and maybe homicide (if you like watching Law and Order re-runs), it’s clutching at straws to teach regicide and fratricide. Unless you’re a student of the Tudors, of course.
Since many roots are only associated with one or two high-frequency English words, there’s no economy of scale: students might as well just learn the vocabulary.
Even if the word part is fairly frequent, it’s not necessarily helpful in figuring out new vocabulary because the connections are often tenuous (from the Latin word for thinness). Can you really figure out the meaning of corrupt by knowing that –rupt- means break? Or convocation from vox (voices)? Or effective from facere (=to do)? As a literary critic, it’s interesting to know that theater comes from the Greek root meaning to see, but how does that help students parse the word theatrical? Yes, if you squint hard enough (ahem), you can see how a particular word got cobbled together from bits and pieces filched from other languages over the centuries, but my students are not studying etymology. They’re just trying to learn English.
I’ve been told that studying word parts is helpful for some standardized tests, such as the verbal portion of GRE, although I suspect there are better ways to use preparation time. And it will definitely help with Scrabble and the National Spelling Bee. As a linguist (from the Latin for tongue), I’m fascinated by philology (Greek: love of learning and literature) and intrigued by neologisms (from a French mashup of Greek parts). But for most ESL students, it’s more effective to focus on learning high-frequency, academic and/or technical or professional vocabulary items along with a small selection of common, productive affixes.
I suspect some readers won’t agree, and honestly I waited months to hit publish on this post because I don’t claim to be a vocabulary expert. Am I missing something?
* Actually, the -ness is a suffix … in Old Norse, per dictionary.com, meaning “provisions for a journey.” Yep, still no help whatsoever.