Whatever = anything or everything; regardless of what
– Whatever you do, don’t forget your grandmother’s birthday.
– Don’t get upset whatever your mother says.
Whenever = every time; at any time; regardless of when
– Whenever we organize a picnic it rains.
– He interrupts me whenever I start to speak.
Wherever = everywhere; no matter where; regardless of where
– Wherever you go you’ll always find someone who speaks English.
– She’ll be happy wherever she decides to live.
Whichever = the person or thing which; no matter which; regardless of which
– Wear whichever shoes are the most comfortable.
– Take whichever one you want.
Whoever = the person who; regardless of who
– Whoever comes with you is welcome.
– Whoever opened the gate didn’t close it.