Norwegian researcher Dr. Dan Olweus and colleagues have conducted concise and comprehensive studies of bullying behavior since the early 1970s, and his is the most commonly quoted definition:
“A person is being bullied when he or she is exposed, repeatedly and over time, to negative actions on the part of one or more other persons. Negative action is when a person intentionally inflicts injury or discomfort upon another person, through physical contact, through words, or in other ways. Note that bullying is both overt and covert” (Olweus, 1991).