The word suffering is sometimes used in the narrow sense of physical pain, but more often it refers to mental or emotional pain, or more often yet to pain in the broad sense, i.e. to any unpleasant feeling, emotion or sensation. The word pain usually refers to physical pain, but it is also a common synonym of suffering. The words pain and suffering are often used both together in different ways. For instance, they may be used as interchangeable synonyms. Or they may be used in 'contradistinction' to one another, as in "pain is physical, suffering is mental", or "pain is inevitable, suffering is optional". Or they may be used to define each other, as in "pain is physical suffering", or "suffering is severe physical or mental pain".
Qualifiers, such as mental, emotional, psychological, and spiritual, are often used for referring to certain types of pain or suffering. In particular, mental pain (or suffering) may be used in relationship with physical pain (or suffering) for distinguishing between two wide categories of pain or suffering. A first caveat concerning such a distinction is that it uses physical pain in a sense that normally includes not only the 'typical sensory experience of physical pain' but also other unpleasant bodily experiences such as itching or nausea. A second caveat is that the terms physical or mental should not be taken too literally: physical pain or suffering, as a matter of fact, happens through conscious minds and involves emotional aspects, while mental pain or suffering happens through physical brains and, being an emotion, involves important physiological aspects.
Unpleasantness, another synonym of suffering or pain in the broad sense, is used in physical pain science to refer to the basic affective dimension of pain (its suffering aspect), usually in contrast with the sensory dimension, as for instance in this sentence from Professor Donald Price: “Pain-unpleasantness is often, though not always, closely linked to both the intensity and unique qualities of the painful sensation.” Words that are roughly synonymous with suffering, in addition to pain and unpleasantness, include distress, sorrow, unhappiness, misery, affliction, woe, ill, discomfort, displeasure, disagreeableness.
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