1. a broad concept that is roughly the equivalent of mental health. Although there are no absolutes and there is considerable cultural variation, some flexible psychological and behavioral criteria can be suggested: (a) freedom from incapacitating internal conflicts; (b) the capacity to think and act in an organized and reasonably effective manner; (c) the ability to cope with the ordinary demands and problems of life; (d) freedom from extreme emotional distress, such as anxiety, despondency, and persistent upset; and (e) the absence of clear-cut symptoms of mental disorder, such as obsessions, phobias, confusion, and disorientation.

2. in statistics, the condition in which a data set presents a normal distribution of values.