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 In recent years, Google’s algorithm became even more advanced, making exact match keyword optimization more and more outdated.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.


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 more: SEO copywriting: the ultimate guide »

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68 Responses to What is keyword stemming?

  1. prasad
    prasad  • 12 months ago

    Great article!

  2. dpblogpl
    dpblogpl  • 12 months ago

    I propose focus on Polish…

    • Marieke van de Rakt

      we have a polish linguist, so it is definitely on our list!

  3. Jutta Lewinsky
    Jutta Lewinsky  • 12 months ago

    Great article! Very informative! Thank you!!! Please add German.

    • Marieke van de Rakt

      German is one of the two languages we have the word forms functionality in!

  4. Alice
    Alice  • 1 year ago

    And French…

    • Marieke van de Rakt

      we’ll put french on our list!

  5. sowmyasri
    sowmyasri  • 1 year ago

    Its good to know about this great article…thanks for sharing, keep updating…

    • Marieke van de Rakt

      you’re welcome!!!

  6. Nishant Maitre
    Nishant Maitre  • 1 year ago

    Thank you for sharing such great article about Keyword Stemming. Keep up the good work.

    • Marieke van de Rakt

      Thank you!!!!

  7. Gyan Ranjan
    Gyan Ranjan  • 1 year ago

    Such a great interesting and useful post about keyword stemming. Yost plugin may help to develop writing skills and attraction to the post.

    • Marieke van de Rakt

      thank you!

  8. Charlie Moger
    Charlie Moger  • 1 year ago

    How does Yoast tell me if a term is “stemmed” per your description? For instance, does Google see AC and Air Conditioning as the stemming?

    • Marieke van de Rakt

      I don’t know whether Google can recognize AC and air conditioning. I would think they do recognize it with their related entities functionality. Read more about related entities in this post: https://yoast.com/regarding-googles-related-entities-patent/
      Using Yoast, I would fill out AC as an synonym for air conditioning.

  9. Wallpaper Australia
    Wallpaper Australia  • 1 year ago

    do you plan to have Yoast plugin and stemming worlds in Hindi ?

    • Marieke van de Rakt

      Hindi is hard, but we like a challenge! It is not on our roadmap yet, though

  10. Lars Henrik Monby
    Lars Henrik Monby  • 1 year ago

    Yes – good to read. I suggest Danish

    • Marieke van de Rakt

      we’ll put in on our list!

  11. Elisabeth Winkler
    Elisabeth Winkler  • 1 year ago

    I read the article with huge interest and, as a writer, love the way good writing is appreciated by search engines, in this case the use of synonyms – which avoid the crime of repetition. But all the way through, I was puzzled: if Google is so good at analysing text, why is a service like Yoast needed? (I know this question shows my ignorance!).

    • Marieke van de Rakt

      That’s such a great question! You made me smile! I think, a good writer does not need our content analysis. But… for most of us, writing is rather hard. You’ll want all the help you can get. Our seo and readability analysis do just that: help you write a better text.

      Besides that, our plugin also takes care of a lot of technical SEO stuff for you. All in all, I highly recommend it:-)

  12. Sergey
    Sergey  • 1 year ago

    Please add Russian language

    • Marieke van de Rakt

      we’ll put it on our list!

  13. Grosir Baju
    Grosir Baju  • 1 year ago

    I hope that Yoast will be able to recognize different word forms properly for Indonesian language. Thank you in advance. Best regards.

    • Marieke van de Rakt

      Indonesian! That’s going to be a hard language, I think. But we like a challenge. Can’t promise anything in a short time frame!

  14. Regina Burdett
    Regina Burdett  • 1 year ago

    Spanish, without a doubt. Please.

    • Marieke van de Rakt

      That’s high on our list of course!

  15. Jim
    Jim  • 1 year ago

    “which language should we tackle next?”

    Why not making an add-on where we can add the keyword stemming words ourselves? The chance that you’re going to do this for Italian, Polish or bahasa Indonesia is almost zero. If keyword stemming is really such a great thing, create the tools for us to join and don’t make us feel left out.

    • Marieke van de Rakt

      I wish it was that simple. Italian and polish will both be tackled at one point. Indonesian is more of challenge for us.

      In order to really recognize word forms, we need to add word list, recognize wordforms in different languages. We have an entire lingo-team (with about 8 linguists) working on these languages.

      What you can do is use our synonyms functionality and additional keyphrases functionality. https://yoast.com/wordpress/plugins/seo/synonyms-related-word-forms-premium/

  16. Shirley George Frazier
    Shirley George Frazier  • 1 year ago

    This topic, which I’ve never considered researching, is quite informative and appreciated, too.

    • Marieke van de Rakt

      thank you!!!

  17. Fred Pietersma
    Fred Pietersma  • 1 year ago

    It should be very useful to translate to the Dutch language also. Maybe I can help you?

    • Marieke van de Rakt

      Maybe you can! Our linguists are currently researching the Dutch language. English and German went rather fast, but they are having much debate about Dutch. It’s a rather hardcore linguists discussion.

      I’ll ask our lingo about contributions from outside Yoast. I’ll get back to you!

  18. Zola Johnson
    Zola Johnson  • 1 year ago

    Thanks for sharing this valuable input about keyword stemming. I guess it’s just a matter of understanding how to use keywords depending on the context in order to rank the content we are sharing.

    • Marieke van de Rakt

      you’re welcome! and you’re right, it is also about understanding on how to use keywords!

  19. Boris Lifanovsky
    Boris Lifanovsky  • 1 year ago

    Would be nice to have Russian as well..

    • Marieke van de Rakt

      russian! I would love to do Russian and we actually have some people from Russia working at Yoast. So we might be able to pull that off!

  20. vahid
    vahid  • 1 year ago

    Persian; please :)

    • Marieke van de Rakt

      that’s going to be a challenge! but I’ll put it on our list!

  21. Lee Hancock
    Lee Hancock  • 1 year ago

    Great post! Synonyms/variations are a great way to increase improve a pages content relevancy. It also allows you expand on a topic without being overly repetitive of the same exact match keyword.

    We start with an exact match term say “Web designers” then look at synonyms and variations that could be included on the page for example

    Web designers > web design agency > web design company > web development company > web design services > website design etc etc

    These are essentially the same thing but just variations. We then look at the next stage and see whether we can add more topical (if relevant) words or whether they are part of another topic that deserves its own page > for example the third level of keywords could be WordPress, HTML5, responsive design etc etc etc

    We find this is getting good organic rankings for pages.

    • Marieke van de Rakt

      thank you!

  22. Felipe
    Felipe  • 1 year ago


    • Marieke van de Rakt

      Portuguese is definitely on our list!

  23. Christine Bonheure
    Christine Bonheure  • 1 year ago

    Yes, please do tackle Dutch! :-)

    • Marieke van de Rakt

      of course :-)

  24. Andrellita Apodaca
    Andrellita Apodaca  • 1 year ago


    • Marieke van de Rakt

      on the list for sure!

  25. Laura
    Laura  • 1 year ago

    It says the Yoast SEO plug-in recognizes the keyword stemming. So If we use a comparable keyword “hotels in XYZ” vs. “hotel in XYZ” that will count toward our overall keyword count in the plugin itself and increase our SEO stoplight score? How new is this? Thanks!

    • Marieke van de Rakt

      great, right?!

  26. Igor Shcherbakov
    Igor Shcherbakov  • 1 year ago

    Your plugin recognizes word forms in Russian

    • Marieke van de Rakt

      not yet!

  27. Mark Samber
    Mark Samber  • 1 year ago

    Great points about stemming in your article. The challenge we SEO professionals have is convincing clients that keywords don’t matter the way they think they do. My clients want to see exact match keywords in their copy and I have to constantly remind them that other semantic markers like intent, keyword stems, context and related or synonymous keywords are what matters from a content perspective. Sure having an exact match occurrence is good, especially in meta titles, urls, and H1s, but writing authoritative and engaging copy doesn’t mean you need to “over salt” the content with exclusively exact match instances of target keywords.

    • Marieke van de Rakt

      I totally get your challenge.
      In our (free) SEO course we have a lesson on what Google wants. It is very basic, perhaps you can use it for your clients to understand it all a little bit better.

  28. alessandro battaglia parodi
    alessandro battaglia parodi  • 1 year ago

    Italian, of course…

    • Marieke van de Rakt


  29. Piotr
    Piotr  • 1 year ago

    Polish. Please!

    • Marieke van de Rakt

      we have a polish linguist working at Yoast! So, it is doable!

  30. Vicky
    Vicky  • 1 year ago

    I hope that Yoast will be able to recognize different word forms properly for Italian language. Thank you in advance. Best regards.

    • Marieke van de Rakt

      Italian! I am actually in Italy right now! we’ll put Italian on our list for sure!

  31. Location de Voiture Casablanca
    Location de Voiture Casablanca  • 1 year ago

    Silly question, but to be clear, the keyword “workout plans and routines guide for women” will actually rank for searches on “workout routines” and “workout guide” even though the specific word order is different? And the idea is to cram as many keywords into the 7 amazon fields as possible?

    • Hanneke
      Hanneke  • 1 year ago


      Word orders don’t matter for Yoast SEO. Stemming however is about bringing a word back to the stem, so it recognizes different word forms. For example, Routine/routines and workout/workouts.
      Hope this answers your question!

      Hanneke – Yoast

  32. satish patil
    satish patil  • 1 year ago

    Very Informative article about keyword and stemming, But Google understands simple English, and whatever you type in Search Query most time answered in Exact match answer, What do you say about this? Then What is the use of variants of keywords?

    • Marieke van de Rakt

      I think the search query the user types into Google is always the most important one. These are the words the user was actually using while searching. I do think Google treats them as very important as well. However, the use of the exact match keyword should never in any way make a post a bad read.

  33. Zai Z
    Zai Z  • 1 year ago

    Do you guys have a plan to make it also available in Bahasa Indonesia, after German? Or perhaps can I help you guys to make that happen? I’d really love to help you even for free. So just drop me an email me at halo[at]zaipad.com

    • Marieke van de Rakt

      I had more people offering help. Indonesian is going to be a challenge. I am going to discuss how we can facilitate contributions to this project outside of Yoast. Thanks so much for offering, that’s very kind!

  34. Wouter Blom
    Wouter Blom  • 1 year ago

    “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.”

    I totally agree. Google might be supersmart. But using an exact match keyword (form) match is still the best way to ensure Google gets it.

    Despite every warning since a decade. Simple tests show that google still needs the exact match variants in the text.

    As long as Google shows very different results for the term “jaloezieen” and “jaloezieën” Google needs all the help ( and exact match use) it can get.

    • Marieke van de Rakt

      I also think that exact match keyword remains important. Especially in dutch. Google isn’t that smart in dutch. the reason why I think exact match keyword is still important is because that is the search query – the exact thing- a person was looking for. These were the words he was using. That means something. That being said, readability is also very important, so you should never go overboard with your keywords.

    • Jose Luis Delgado
      Jose Luis Delgado  • 1 year ago

      So it’s ok to use synonyms correct? I guess as long as we don’t over do it. lol.