Pain is a sensation felt from the introduction of stimuli to the human body. It is an unpleasant and distressing sensation, although not for a select few. The sensation of pain is measured relatively. Different people have varying levels of tolerance to pain, and so a set standard for measuring pain is almost impossible to calculate. Of course there is generally a distinct difference between receiving a light punch and getting hit by a car.
The word pain takes its roots from a variety of older languages. From the Anglo-Norman paine, peigne, penne, pain, pein, peyene to the Middle French peine, paine, peinne, pene, there seems to be no end to the lexical iterations of the same word. Common phrases such as “upon pain of”, or “to take pains” also have their sources in Old French; they are “sur peine de” (c1340) and “prendre la peine” (c1461-9) respectively. Pain can also be used as a verb. In this context it means to exert or inflict something painful. For example “it pained her to write this gloss” is an adequate representation of the verbal form of pain. Like the noun pain, the verb also has similar roots, peiner, painer, pener, and pener. Unexpectedly, pain is also the name of a kind of bread, or to be more specific, a type of rissole. This definition of the word originates from the classical Latin pānis bread. Think panini.
Historically, Aristotle believed that pain was the sensation caused by evil spirits entering a body after an injury. Hippocrates hypothesized that pain was instead caused by an imbalance of the various vital fluids in the body.
Medically speaking there are three types of pain – nociceptive, neuropathic and psychogenic. Nociceptive and neuropathic pain is pain that is generally associated to be physical, while psychogenic pain is emotional and mental. Because of the fact that all three kinds of pain are vastly different, there is no common ground to compare each of them. A sufferer of acute nociceptive pain may feel extreme agony, but as soon as the stimulus causing that pain is removed, the pain immediately subsides. This is opposed to sufferers of emotional trauma or long term illnesses that may or may not ever heal. How can you compare which is worse? Especially since psychogenic sufferers are often denounced by some medical professionals who believe a mental source of pain isn’t real.
Pain is also separated into two different time categories, acute and chronic pain; the former being short term, and the latter long term. A curious form of chronic pain is called phantom pain. It is pain that occurs in a limb or organ that is no longer a physical part of the body. Phantom pain is frequently found in amputees who experience varying levels of discomfort in their missing limb.
"pain, n1." OED Online, accessed November 19, 2012, Oxford University Press. http://www.oed.com/view/Entry/136058?rskey=ukaU0H&result=3&isAdvanced=false#eid
"pain, n2." OED Online, accessed November 19, 2012, Oxford University Press. http://www.oed.com/view/Entry/136057?rskey=ukaU0H&result=2&isAdvanced=false#eid
"pain, v." OED Online, accessed November 19, 2012, Oxford University Press. http://www.oed.com/view/Entry/136058?rskey=ukaU0H&result=3&isAdvanced=false#eid