Elasticsearch allows you to configure a scoring algorithm or similarity per
similarity setting provides a simple way of choosing a similarity
algorithm other than the default TF/IDF, such as
Similarities are mostly useful for
string fields, especially
analyzed string fields, but can also apply to other field types.
Custom similarites can be configured by tuning the parameters of the built-in similarities. For more details about this expert options, see the similarity module.
The only similarities which can be used out of the box, without any further configuration are:
similarity can be set on the field level when a field is first created,