add synonym token filter docs #8447

_analyzers/token-filters/index.md

@@ -55,7 +55,7 @@ Normalization | `arabic_normalization`: [ArabicNormalizer](https://lucene.apache
 `stemmer` | N/A | Provides algorithmic stemming for the following languages in the `language` field: `arabic`, `armenian`, `basque`, `bengali`, `brazilian`, `bulgarian`, `catalan`, `czech`, `danish`, `dutch`, `dutch_kp`, `english`, `light_english`, `lovins`, `minimal_english`, `porter2`, `possessive_english`, `estonian`, `finnish`, `light_finnish`, `french`, `light_french`, `minimal_french`, `galician`, `minimal_galician`, `german`, `german2`, `light_german`, `minimal_german`, `greek`, `hindi`, `hungarian`, `light_hungarian`, `indonesian`, `irish`, `italian`, `light_italian`, `latvian`, `Lithuanian`, `norwegian`, `light_norwegian`, `minimal_norwegian`, `light_nynorsk`, `minimal_nynorsk`, `portuguese`, `light_portuguese`, `minimal_portuguese`, `portuguese_rslp`, `romanian`, `russian`, `light_russian`, `sorani`, `spanish`, `light_spanish`, `swedish`, `light_swedish`, `turkish`.
 `stemmer_override` | N/A | Overrides stemming algorithms by applying a custom mapping so that the provided terms are not stemmed.
 `stop` | [StopFilter](https://lucene.apache.org/core/8_7_0/core/org/apache/lucene/analysis/StopFilter.html) | Removes stop words from a token stream.
-`synonym` | N/A | Supplies a synonym list for the analysis process. The synonym list is provided using a configuration file.
+[`synonym`]({{site.url}}{{site.baseurl}}/analyzers/token-filters/synonym/) | N/A | Supplies a synonym list for the analysis process. The synonym list is provided using a configuration file.
 `synonym_graph` | N/A | Supplies a synonym list, including multiword synonyms, for the analysis process.
 `trim` | [TrimFilter](https://lucene.apache.org/core/9_10_0/analysis/common/org/apache/lucene/analysis/miscellaneous/TrimFilter.html) | Trims leading and trailing white space from each token in a stream. 
 `truncate` | [TruncateTokenFilter](https://lucene.apache.org/core/9_10_0/analysis/common/org/apache/lucene/analysis/miscellaneous/TruncateTokenFilter.html) | Truncates tokens whose length exceeds the specified character limit. 

_analyzers/token-filters/synonym.md

@@ -0,0 +1,277 @@
+---
+layout: default
+title: Synonym
+parent: Token filters
+nav_order: 420
+---
+
+# Synonym token filter
+
+The `synonym` token filter allows you to map multiple terms to a single term or create equivalence groups between words, improving search flexibility.
+
+## Parameters
+
+The `synonym` token filter can be configured with the following parameters.
+
+Parameter | Required/Optional | Data type | Description
+:--- | :--- | :--- | :--- 
+`synonyms` | Either `synonyms` or `synonyms_path` needs to be configured | String | List of synonym rules defined directly in the configuration.
+`synonyms_path` | Either `synonyms` or `synonyms_path` needs to be configured | String | File path to synonym rules, absolute or relative to config directory.
+`lenient` | Optional | Boolean | Ignore the exceptions when loading the rule configurations. Default is `false`.
+`format` | Optional | String | Specifies which format is used to determine how synonyms are defined and interpreted by OpenSearch. Options are: `solr` or [`wordnet`](https://wordnet.princeton.edu/). Default is `solr`.
+`expand` | Optional | Boolean |  Expand equivalent synonym rules. Default is `false`.<br><br>For example: <br>If `expand` is set to `true` with synonym defined as `"quick, fast"`, the synonym rules are configured as follows:<br>- quick => quick<br>- quick => fast<br>- fast => quick<br>- fast => fast<br><br>If `expand` is set to `false`, the synonym rules are configured as follows:<br>- quick => quick<br>- fast => quick
+
+## Example using solr format
+
+The following example request creates a new index named `my-synonym-index` and configures an analyzer with `synonym` filter with default `solr` rules format:
+
+```json
+PUT /my-synonym-index
+{
+  "settings": {
+    "analysis": {
+      "filter": {
+        "my_synonym_filter": {
+          "type": "synonym",
+          "synonyms": [
+            "car, automobile",
+            "quick, fast, speedy",
+            "laptop => computer"
+          ]
+        }
+      },
+      "analyzer": {
+        "my_synonym_analyzer": {
+          "type": "custom",
+          "tokenizer": "standard",
+          "filter": [
+            "lowercase",
+            "my_synonym_filter"
+          ]
+        }
+      }
+    }
+  }
+}
+```
+{% include copy-curl.html %}
+
+## Generated tokens
+
+Use the following request to examine the tokens generated using the analyzer:
+
+```json
+GET /my-synonym-index/_analyze
+{
+  "analyzer": "my_synonym_analyzer",
+  "text": "The quick dog jumps into the car with a laptop"
+}
+```
+{% include copy-curl.html %}
+
+The response contains the generated tokens:
+
+```json
+{
+  "tokens": [
+    {
+      "token": "the",
+      "start_offset": 0,
+      "end_offset": 3,
+      "type": "<ALPHANUM>",
+      "position": 0
+    },
+    {
+      "token": "quick",
+      "start_offset": 4,
+      "end_offset": 9,
+      "type": "<ALPHANUM>",
+      "position": 1
+    },
+    {
+      "token": "fast",
+      "start_offset": 4,
+      "end_offset": 9,
+      "type": "SYNONYM",
+      "position": 1
+    },
+    {
+      "token": "speedy",
+      "start_offset": 4,
+      "end_offset": 9,
+      "type": "SYNONYM",
+      "position": 1
+    },
+    {
+      "token": "dog",
+      "start_offset": 10,
+      "end_offset": 13,
+      "type": "<ALPHANUM>",
+      "position": 2
+    },
+    {
+      "token": "jumps",
+      "start_offset": 14,
+      "end_offset": 19,
+      "type": "<ALPHANUM>",
+      "position": 3
+    },
+    {
+      "token": "into",
+      "start_offset": 20,
+      "end_offset": 24,
+      "type": "<ALPHANUM>",
+      "position": 4
+    },
+    {
+      "token": "the",
+      "start_offset": 25,
+      "end_offset": 28,
+      "type": "<ALPHANUM>",
+      "position": 5
+    },
+    {
+      "token": "car",
+      "start_offset": 29,
+      "end_offset": 32,
+      "type": "<ALPHANUM>",
+      "position": 6
+    },
+    {
+      "token": "automobile",
+      "start_offset": 29,
+      "end_offset": 32,
+      "type": "SYNONYM",
+      "position": 6
+    },
+    {
+      "token": "with",
+      "start_offset": 33,
+      "end_offset": 37,
+      "type": "<ALPHANUM>",
+      "position": 7
+    },
+    {
+      "token": "a",
+      "start_offset": 38,
+      "end_offset": 39,
+      "type": "<ALPHANUM>",
+      "position": 8
+    },
+    {
+      "token": "computer",
+      "start_offset": 40,
+      "end_offset": 46,
+      "type": "SYNONYM",
+      "position": 9
+    }
+  ]
+}
+```
+
+## Example using WordNet format
+
+The following example request creates a new index named `my-wordnet-index` and configures an analyzer with `synonym` filter with [`wordnet`](https://wordnet.princeton.edu/) rules format:
+
+```json
+PUT /my-wordnet-index
+{
+  "settings": {
+    "analysis": {
+      "filter": {
+        "my_wordnet_synonym_filter": {
+          "type": "synonym",
+          "format": "wordnet",
+          "synonyms": [
+            "s(100000001,1,'fast',v,1,0).",
+            "s(100000001,2,'quick',v,1,0).",
+            "s(100000001,3,'swift',v,1,0)."
+          ]
+        }
+      },
+      "analyzer": {
+        "my_wordnet_analyzer": {
+          "type": "custom",
+          "tokenizer": "standard",
+          "filter": [
+            "lowercase",
+            "my_wordnet_synonym_filter"
+          ]
+        }
+      }
+    }
+  }
+}
+```
+{% include copy-curl.html %}
+
+## Generated tokens
+
+Use the following request to examine the tokens generated using the analyzer:
+
+```json
+GET /my-wordnet-index/_analyze
+{
+  "analyzer": "my_wordnet_analyzer",
+  "text": "I have a fast car"
+}
+```
+{% include copy-curl.html %}
+
+The response contains the generated tokens:
+
+```json
+{
+  "tokens": [
+    {
+      "token": "i",
+      "start_offset": 0,
+      "end_offset": 1,
+      "type": "<ALPHANUM>",
+      "position": 0
+    },
+    {
+      "token": "have",
+      "start_offset": 2,
+      "end_offset": 6,
+      "type": "<ALPHANUM>",
+      "position": 1
+    },
+    {
+      "token": "a",
+      "start_offset": 7,
+      "end_offset": 8,
+      "type": "<ALPHANUM>",
+      "position": 2
+    },
+    {
+      "token": "fast",
+      "start_offset": 9,
+      "end_offset": 13,
+      "type": "<ALPHANUM>",
+      "position": 3
+    },
+    {
+      "token": "quick",
+      "start_offset": 9,
+      "end_offset": 13,
+      "type": "SYNONYM",
+      "position": 3
+    },
+    {
+      "token": "swift",
+      "start_offset": 9,
+      "end_offset": 13,
+      "type": "SYNONYM",
+      "position": 3
+    },
+    {
+      "token": "car",
+      "start_offset": 14,
+      "end_offset": 17,
+      "type": "<ALPHANUM>",
+      "position": 4
+    }
+  ]
+}
+```