What is keyword stemming?

Google can read and analyze texts very well. Google understands that ‘walk’, walking’, ‘walked’, ‘walks’ all boils down to the same thing. Also, Google knows that ‘baby’ is basically the same thing as babies. Optimizing your text for an exact match keyword isn’t a very smart thing to do. That’s why we introduced word form recognition in Yoast SEO Premium. You can now optimize your post and we’ll analyze the different word forms like walk, walks and walking. For longer tail keywords, we also recognize the words if you decide to use them in a different word order.

So, at Yoast, we talk about word forms, sometimes also about morphology recognition. At the same time, I hear the linguists at Yoast talking about keyword stemming too. And I noticed some SEOs talked about it as well. But what is keyword stemming? How does stemming relate to morphology recognition? And what does it have to do with SEO? I’ll explain all about it in this post.

What is stemming?

Stemming or keyword stemming refers to Google’s ability to understand different word forms of a specific search query. It is called stemming because it comes from the word stem, base or root form. If you use the word ‘buy’ in a sentence, a stemming algorithm would recognize the words ‘buys’, ‘buying’ and ‘bought’ as variations of the word ‘buy’ as well. Some SEOs also differ between stemming and lemmatization.

Google has used keyword stemming in its algorithms for a long time now. The first blog posts about it from SEO experts like Rand Fishkin and Bill Slawski go as far back as 10 years ago. For languages other than English, Google began recognizing word forms much later. In recent years, Google’s algorithm became even more advanced, making exact match keyword optimization more and more outdated.

If you want to optimize your text for the term ballet shoes, for example, you should be able to use the term ballet shoe as well. Google understands that ballet shoes and ballet shoe are basically the same thing. Our Yoast SEO Premium plugin recognizes both word forms as well (at least in English and, since Yoast SEO 10.1, in German).

Stemming and word forms

If people are talking about keyword stemming or a stemming algorithm, they mean that the algorithm is able to recognize different word forms of a certain keyword. That’s exactly what the word forms functionality in Yoast SEO does. We do not automatically detect synonyms, but we do allow you to enter synonyms and we’ll take them into account in our SEO analysis.

Maybe we should have called our word forms functionality stemming. But it’s a difficult word to explain to people. So, that’s why we’ll stick with word forms.

Stemming and SEO

Google has become very smart. It understands texts. It understands context. In order to stand a chance in the search engines, you need to write awesome texts that show your authority on a certain subject. Content stuffed with keywords does not rank anymore. Google hates that, users hate that.

You need to use synonyms and related keywords in your content to make it pleasant to read and to make it rank! You need to use different word forms in order to write a post that is nice to read. Thanks to stemming, we can tell that they belong together. Read more about it in our post about our word form analysis.

Conclusion

The SEO industry has been talking about stemming and lemmatization for over a decade. Our linguists talk about it too. For good reason, because stemming allows them to recognize different word forms. This isn’t “easy”. At Yoast, we have an entire team of linguists working on our SEO and readability analyses. We’re now able to recognize different word forms properly for both English and German. We’re already working on new languages, I know Dutch is high on our list — probably because it’s our native language. Do let me know: which language should we tackle next?

Read on: SEO copywriting: the ultimate guide »

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