You use whichever in order to indicate that it does not matter which of the possible alternatives happens or is chosen. Israel offers automatic citizenship to all Jews who want it, whatever colour they are and whichever language they speak. = whatever Whichever is also a conjunction. We will gladly exchange your goods, or refund your money, whichever you prefer. = whatever
Whether one or another; whether one or the other; which; that one (of two or more) which; as, whichever road you take, it will lead you to town
Any number of a group. It may be preferrable to use whoever or whomever (depending on which is the correct usage) when it involves one or more person(s)
You use whichever to specify which of a number of possibilities is the right one or the one you mean. learning to relax by whichever method suits you best. Whichever is also a conjunction. Fishing is from 6 am to dusk or 10.30pm, whichever is sooner