$lexical in collections

This string is indexed and used for lexicographical matching and the lexical search component of hybrid search.

Only collections that have lexical enabled support the $lexical field. For more information, see Create a collection that supports lexicographical matching.

To be included in a hybrid search, a document must have both the $lexical field and the $vector field populated.

For examples of populating the $lexical field, see Insert a document and Insert documents.