When words refer to stimuli or events that are painful or aversive, those words themselves may become painful or aversive. That is, their functions will be transformed according to their relation of equivalence to the actual stimuli or events. This process is why it can be painful and aversive to think of a dead loved one, or recall childhood abuse, or reflect on your failures, or talk about your sadness. And it allows us to “carry” the pain of aversive events for a lifetime, and experience it at virtually any time or place.