Merriam-Webster Collegiate Dictionary - pain

 I. noun  Etymology: Middle English, from Anglo-French peine, from Latin poena, from Greek poine payment, penalty; akin to Greek tinein to pay, tinesthai to punish, Avestan kaena revenge, Sanskrit cayate he revenges  Date: 14th century  1. punishment  2.  a. usually localized physical suffering associated with bodily disorder (as a disease or an injury); also a basic bodily sensation induced by a noxious stimulus, received by naked nerve endings, characterized by physical discomfort (as pricking, throbbing, or aching), and typically leading to evasive action  b. acute mental or emotional distress or suffering ; grief  3. plural the throes of childbirth  4. plural trouble, care, or effort taken to accomplish something was at ~s to reassure us  5. one that irks or annoys or is otherwise troublesome — often used in such phrases as ~ in the neck  • ~less adjective  • ~lessly adverb  • ~lessness noun  II. verb  Date: 14th century  transitive verb  1. to make suffer or cause distress to ; hurt  2. archaic to put (oneself) to trouble or exertion  intransitive verb  1. archaic suffer  2. to give or have a sensation of ~