If you are asking about abnormal behavior from a sociological point of view, then the first point you need to realize is that all societies or culture have differences. This is so, because societies are created by people. Therefore, what is abnormal in one area may be quite normal in another area. Great scholars have done research on this. Even things that seem universal, like gender, are variable. Clifford Geertz shows pretty convincingly that societies differ greatly when it comes to hermaphrodites. Some groups see them as powerful and special and some groups see them as a serious aberration of society. The point is that notions of normality differ greatly. Mary Bread has also done a lot of work in this area as she looks a liminal things or things that fall between classifications. She argues that these too are viewed differently from culture to culture. I will add a few sociological angles to consider.
Abnormal behavior is a term applied to describe any type of behavior, positive or negative, that is out of the social, physical, or emotional norm. For example a person who is who takes all of his money and gives it all to the poor can be considered abnormal. Society dictates what behaviors are considered abnormal. In American culture it is quite normal to kiss on the mouth, but in some cultures it is considered to be disgusting abnormal behavior.
In the psychology sector the DSM manual is used to determine the classification of behavior with the use of specific tests including a person's social history. The tests take in to consideration that a person who is grieving is going to respond different on the tests that someone who not grieving. It is not abnormal for a grieving person to feel sad and despondent, but it would be for a five year old child in a seemingly happy well functioning family.
Axis I: Clinical disorders caused by stress related issues in a client/person's life
Axis II: Personality disorders-maladaptive ways of responding to other people
Mental Retardation/Intellectual functioning below a full scale IQ score of 72
Axis III: General medical conditions
Axis IV: Psychosocial and environmental problems
Axis V: Global assessment of functioning