Merriam-Webster's Collegiate® Dictionary, 11th Edition
PAIN
I. noun
Etymology: Middle English, from Anglo-French peine, from Latin poena, from Greek poinē payment, penalty; akin to Greek tinein to pay, tinesthai to punish, Avestan kaēnā revenge, Sanskrit cayate he revenges
Date: 14th century
punishment ,
2. usually localized physical suffering associated with bodily disorder (as a disease or an injury), acute mental or emotional distress or suffering ; grief , the throes of childbirth, trouble, care, or effort taken to accomplish something , one that irks or annoys or is otherwise troublesome, painless adjective painlessly adverb painlessness noun
II. verb
Date: 14th century
transitive verb to make suffer or cause distress to ; hurt , to put (oneself) to trouble or exertion, intransitive verb suffer , to give or have a sensation of pain