The criteria that researchers use to classify aggressive behaviour as bullying are "repetition", "power imbalance", and "intent to hurt". However, studies that have analyzed adolescents' perceptions of bullying find that most adolescents do not simultaneously consider these three criteria. This paper examines adolescents' perceptions of bullying and of the different forms it takes, and whether these perceptions vary according to the teen's role of victim, aggressor, or witness in a bullying situation. The data acquisition instrument was a questionnaire applied to a sample of 2295 teenagers. The results show that none of these three groups considered the criterion of repetition to be important to define bullying. A further conclusion was that both aggressors and witnesses used the criteria of "power imbalance" and "intent to hurt" to identify a situation of bullying, although the aggressors placed especial emphasis on the superiority of power over the victim, while the witnesses emphasized the intent to hurt the victim. One noteworthy finding was that victims do not consider the factor "power imbalance". The factor that determined their perceptions was the "intent to hurt". Finally, some modes of bullying were seen as forms of typical teen social interactions, and the perception depended significantly on the adolescent's role as aggressor, victim, or witness. (Contains 5 tables.)