Almost Similar Page Titles Help / Question
Fragment of a discussion from Project:Support desk
If we're talking only about search, and not people entering a page name directly, then there is an extension for addressing case sensitivity in searches - Extension:TitleKey.
You may also want to enable $wgEnableMWSuggest to allow search suggestions - which can help with singular vs plural.
Keep in mind that the MWSuggest and Titleykey will not address variations in wikilinks - so TREES may go to Trees via the search, but [[TREES]] will be a redlink. Redirects can be used for common variations (singular vs plural as one example) where a page title may be used directly in things like the URL or wikilinks.
