boost

Individual fields can be boosted automatically — count more towards the relevance score — at query time, with the boost parameter as follows:

PUT my_index
{
  "mappings": {
    "_doc": {
      "properties": {
        "title": {
          "type": "text",
          "boost": 2 
        },
        "content": {
          "type": "text"
        }
      }
    }
  }
}

You can achieve the same effect by using the boost parameter directly in the query, for instance the following query (with field time boost):

POST _search
{
    "query": {
        "match" : {
            "title": {
                "query": "quick brown fox"
            }
        }
    }
}

is equivalent to:

POST _search
{
    "query": {
        "match" : {
            "title": {
                "query": "quick brown fox",
                "boost": 2
            }
        }
    }
}

The boost is also applied when it is copied with the value in the _all field. This means that, when querying the _all field, words that originated from the title field will have a higher score than words that originated in the content field. This functionality comes at a cost: queries on the _all field are slower when field boosting is used.