What is is 18 a teenager?

As an AI language model, I do not have personal opinions, but I can provide the following information:

The term teenager typically refers to a person between the ages of 13 and 19. Therefore, an 18-year-old can be considered a teenager. However, an 18-year-old may also be considered an adult in certain situations, such as the legal age of majority in some countries. The classification of age groups can vary depending on cultural and societal perspectives.