This is part of the difference between series.
I’ve heard some people confusing the words whatever and whichever. Here’s the difference between the two.
Whatever
We use whatever when the options are unknown.
- Take whatever you want.
- Tell me whatever you feel comfortable with.
- Whatever I try ends up a disaster.
Whichever
We use whichever when the options are known and limited.
- Take whichever apple you want.
- Use whichever green hat seems to suit you.
- Pick whichever chocolate bar you’d like.
The easiest way to remember the difference between these two words is that which sort of sounds like each, and that implies limited choice.