Abnormal behavior has a variety of technician definitions, but it generally refers to actions that are counter to convention. An adult talking to an imaginary friend is abnormal because it is rare adult behavior. Abnormal psychology is a branch of psychology where professionals study mental health conditions that drive abnormal behaviors.
Parents and teachers evaluate mental, social and behavioral development in young children to identify abnormal behaviors and their causes. Early detection of abnormal development is important to training and development intervention.
Scientists take a technical perspective and view abnormal behaviors as an action that deviates from the statistical norm. If only 10 percent of the general population like to eat beets for supper, for instance, eating beets for supper is a statistically abnormal behavior. In this instance, "abnormal" doesn't necessarily equate to problematic.
A person can behave abnormally in ways that convey maturity or superiority with certain skills. A young adult choosing not to drink is often viewed as abnormal behavior, but this choice may offer health, career and financial advantages.
An "eccentric" person demonstrates abnormal behaviors and tendencies. Eccentrics do things that most people find odd or peculiar. A person with 40 cats in her home might become known as the "eccentric cat lady" in the neighborhood.