A romantic affair between a student and a teacher, usually from the same class in the same school. Although not law breaking, student-teacher dating relationships are generally considered to be unprofessional if not immoral. In the U.S., it's also illegal if the affair involves physical relationship with a student who is under 18 years of age. Teachers usually try to avoid student-teacher romance for fear of damaged reputations and/or losing their teaching positions. Many student-teacher affairs have been the subject of multi-million lawsuits.