The words «juvenile» and «adolescent» are often used in everyday speech and writing as if they are synonymous. Used correctly there are differences between these words and the life history biology they represent. In common usage the adjective «juvenile» refers to is a young person, older than a child but not showing clear signs of sexual or social maturation. Often such juveniles are pre-teen in age. People of any age may be described as showing juvenile behaviour or attitudes, meaning immature, inexperienced, unsophisticated, naïve, foolish, or silly. The adjective «adolescent» commonly means characteristic of, or relating to, or undergoing sexual and social maturation. As nouns the difference in common usage between «juvenile» and «adolescent» is that the juvenile is a prepubescent child while adolescent is a teenager and a person a after puberty.

In this Gallery the common usages of these terms is refined to apply to life history biology. The pre-puberty nature of the juvenile versus the post-puberty nature of the adolescent is an essential life history difference, which come with behavioural, social, economic, cognitive, and sexual consequences. [Barry Bogin]