An unpleasant experience associated with actual or potential tissue damage, or described in terms of such damage.
Pain is always subjective.
Each individual learns the application of the word through experiences in early life. Because it is always unpleasant, pain is an emotional, as well as a sensory experience. This definition avoids tying pain to the stimulus. Activity induced in peripheral nerve fibres is not pain, which is always a psychological state. As nerve impulses pass from the peripheral nerves into the spinal cord, they pass through a gate control in which the subsequent passage of the impulse depends on the mixture of the various events in the periphery and on descending controls from the brain, which permit the entry and transmission of the information.