This definition is helpful in identifying those with mental health issues and focuses a lot on an individual's external behaviour. Every society has their standards of what they consider to be 'normal' behaviour and deviating from these can be seen as abnormal.
In England for example, we condemn swearing in front of young children and deviating from this Is highly frowned upon, therefore if somebody does they are considered as 'abnormal' as they are breaking the fundamental social rules (norms) of our society.
Another example of a more common 'social norm' is dressing smartly for a job interview and being polite to your potential new boss. Imagine you're the interviewer and you interview someone who has arrived late and presented themselves in a very lazy manner; you'd immediately form the impression that this person is abnormal.
Cultures do vary throughout different societies though, therefore there isn't one universal set of rules; this is known as 'cultural relativism'. What can be considered normal in one culture can be interpreted as highly abnormal in another. Consequently an individual could be labelled as mentally ill of 'abnormal'. This is a limitation of this definition of abnormality because It could mean people could misread another's behaviour as 'abnormal' when maybe that just follow another culture etc.
An example of where people could misinterpret another's behaviour and class it as 'abnormal' (due to cultural reasons) is when a French citizen for example, pushes to the front of a bus que in England; this is classed as normal in France, however, in England the majority of people of whom have grown up in our society define that as being rude or 'abnormal' behaviour, consequently, that French citizen is labelled as deviating from social norms.
Another limitation of this definition of abnormality is that it changes over time; we haven't always had the same set of fundamental rules of society throughout time. It's often contextual to...