In English, how do they differ; - shrivel, wilt & wither?

Shrivel is to dry out. It applies to things like raisins or skin (the way fingers get after being immersed in water for a long time). Wilting usually applies to plants that don't get enough water. Their leaves "wilt" and droop. Wither means to waste away or disintegrate. You would say that someone who is losing too much weight is "withering" away. These aren't dictionary definitions but hopefully it helps clear it up!