I'm using the English.Lucene analyzer, searching for the term 'rocking chairs' correctly returns results such as rocking chair
but does not return results such as rocker
What can I do to tune the index so that it returns these results?
You can use a Synonym map https://learn.microsoft.com/en-us/azure/search/search-synonyms and map rocking to rocker so that results with rocker are also returned.