Deviation from social norms
Groups of people define behaviour as 'abnormal' on the basis that if offends their sense of what is acceptable, or the norm. People make a collective judgement about what is right/normal based on implicit and explicit social norms.
Social norms are specific to the culture we live in, so there are relatively few behaviours that would be considered universally abnormal on the basis that they break social norms. For example, homosexuality is illegal and viewed as abnormal in some cultures and was considered abnormal in the UK until recently.
Example: antisocial personality disorder - a…