elasticsearch/docs/reference/text-analysis/analysis-stemmer-tokenfilter.md

---

navigation_title: "Stemmer" mapped_pages:

• https://www.elastic.co/guide/en/elasticsearch/reference/current/analysis-stemmer-tokenfilter.html ---

Stemmer token filter [analysis-stemmer-tokenfilter]

Provides algorithmic stemming for several languages, some with additional variants. For a list of supported languages, see the language parameter.

When not customized, the filter uses the porter stemming algorithm for English.

Example [analysis-stemmer-tokenfilter-analyze-ex]

The following analyze API request uses the stemmer filter’s default porter stemming algorithm to stem the foxes jumping quickly to the fox jump quickli:

GET /_analyze
{
  "tokenizer": "standard",
  "filter": [ "stemmer" ],
  "text": "the foxes jumping quickly"
}

The filter produces the following tokens:

[ the, fox, jump, quickli ]

Add to an analyzer [analysis-stemmer-tokenfilter-analyzer-ex]

The following create index API request uses the stemmer filter to configure a new custom analyzer.

PUT /my-index-000001
{
  "settings": {
    "analysis": {
      "analyzer": {
        "my_analyzer": {
          "tokenizer": "whitespace",
          "filter": [ "stemmer" ]
        }
      }
    }
  }
}

Configurable parameters [analysis-stemmer-tokenfilter-configure-parms]

$$$analysis-stemmer-tokenfilter-language-parm$$$

language : (Optional, string) Language-dependent stemming algorithm used to stem tokens. If both this and the name parameter are specified, the language parameter argument is used.

:::{dropdown} Valid values for language

Valid values are sorted by language. Defaults to english. Recommended algorithms are bolded.

• Arabic: arabic
• Armenian: armenian
• Basque: basque
• Bengali:bengali
• Brazilian Portuguese:brazilian
• Bulgarian:bulgarian
• Catalan:catalan
• Czech:czech
• Danish:danish
• Dutch
  • dutch
  • dutch_kp :::{admonition} Deprecated in 8.16.0 This language was deprecated in 8.16.0. :::
• English:
  • english
  • light_english
  • lovins :::{admonition} Deprecated in 8.16.0 This language was deprecated in 8.16.0. :::
  • minimal_english
  • porter2
  • possessive_english
• Estonian:estonian
• Finnish:
  • finnish
  • light_finnish
• French:
  • light_french
  • french
  • minimal_french
• Galician:
  • galician
  • minimal_galician (Plural step only)
• German:
  • light_german,
  • german
  • minimal_german
• Greek:greek
• Hindi:hindi
• Hungarian:
  • hungarian
  • light_hungarian
• Indonesian:indonesian
• Irish:irish
• Italian:
  • light_italian
  • italian
• Kurdish (Sorani):sorani
• Latvian:latvian
• Lithuanian:lithuanian
• Norwegian (Bokmål):
  • norwegian
  • light_norwegian
  • minimal_norwegian
• Norwegian (Nynorsk):
  • light_nynorsk
  • minimal_nynorsk
• Persian:persian
• Portuguese:
  • light_portuguese
  • minimal_portuguese
  • portuguese
  • portuguese_rslp
• Romanian:romanian
• Russian:
  • russian
  • light_russian
• Serbian:serbian
• Spanish:
  • light_spanish
  • spanish
  • spanish_plural
• Swedish:
  • swedish
  • light_swedish
• Turkish:turkish :::

name : An alias for the language parameter. If both this and the language parameter are specified, the language parameter argument is used.

Customize [analysis-stemmer-tokenfilter-customize]

To customize the stemmer filter, duplicate it to create the basis for a new custom token filter. You can modify the filter using its configurable parameters.

For example, the following request creates a custom stemmer filter that stems words using the light_german algorithm:

PUT /my-index-000001
{
  "settings": {
    "analysis": {
      "analyzer": {
        "my_analyzer": {
          "tokenizer": "standard",
          "filter": [
            "lowercase",
            "my_stemmer"
          ]
        }
      },
      "filter": {
        "my_stemmer": {
          "type": "stemmer",
          "language": "light_german"
        }
      }
    }
  }
}