Young-adult fiction or young adult literature, often termed as YA, is fiction written, published, or marketed to adolescents and young adults. The Young Adult Library Services Association (YALSA) of the American Library Association (ALA) defines a young adult as someone between the ages of twelve and eighteen. Authors and readers of young adult (YA) novels often define the category as literature traditionally written for ages ranging from sixteen years to the age of twenty-five, while Teen Fiction is written for the ages of ten to fifteen. The terms young-adult novel, juvenile novel, young-adult book, etc. refer to the works in the YA category. The subject matter and story lines of YA literature are typically consistent with the age and experience of the main character, but YA literature spans the spectrum of fiction genres. YA stories that focus on the specific challenges of youth are sometimes referred to as problem novels or coming-of-age novels.