Target Keywords – effect of ‘Plurals’

So a target keyword (phrase) I have is ‘harmony necklace’ … I rank a couple of places higher for search term Harmony Necklaces than Harmony Necklace which is the key target because it has double the searches – does the fact that my Categories use the plural ‘necklaces‘, e.g. category = Full Range of Harmony Necklaces. this is reflected in the url’s, domain/category/product title.

Or would it be better to rename the category to ‘Harmony Necklace – Full Range’ ?? and so on for the other categories.