https://www.greatvaluecolleges.net/faq/what-is-a-nontraditional-student/

The National Center for Education Statistics (NCES) maintains a list of seven different characteristics of nontraditional students. They range from delayed college enrollment, to part-time studies combined with full-time work, to being a single parent, or simply the lack of a high school diploma. The original definition for nontraditional students only referred to the student being over age 25 when entering college. With about half of current students ranging in age from 25 to 75, being a nontraditional student is no longer rare or unusual, if it ever was.