IPA: /wɪˈtʃɛvər/
KK: /wɪtʃˈɛvər/
Referring to any one or more from a set of options without specifying which one.
You can choose whichever book you like from the shelf.
A word used to refer to any one or more items from a group without specifying which one.
You can choose whichever book you like from the shelf.
Whichever is formed from "which" (from Old English "hwilc", meaning what one or what kind) and "-ever" (meaning at any time or in any case). The word "whichever" refers to any one or any kind of something from a specified set.
Think of 'which' to remember that 'whichever' means any one from a selection.
No commonly confused words.