Teenage veut littéralement dire en anglais, les âges en teen ou pratiquement se terminant par teen, donc de treize à dix-neuf, ce qui revient à l'adolescence. Le terme teen est équivalent et plus actuel. Le teenager désigne l'adolescent.
Adolescence is a transitional stage of physical and psychological development that generally occurs during the period from puberty to adulthood. Adolescence is usually associated with the teenage years, but its physical, psychological or cultural expressions may begin earlier and end later. Puberty now typically begins during preadolescence, particularly in females. Physical growth and cognitive development can extend into the early 20s. Age provides only a rough marker of adolescence, and scholars have not agreed upon a precise definition. Traditionally, it includes ages 10 to 19, but an expansive definition includes ages 10 to 24 to account for a more comprehensive understanding of this phase of life.