My interest in definitions grew from my experiences teaching "educable mentally retarded," "disabled reader," and "emotionally disturbed" (as they were known at that time) students. As a novice teacher, I was struck by the similarities more than differences among these students in the different selfcontained special education classrooms where I worked. As a doctoral student at the Pennsylvania State University and as a professor, I spent time studying issues in identification and assessment practices in special education. Defining Emotional Disturbance and Identifying Disturbed Behavior In special education, a definition creates a condition and identification practices bring it to life. Emotional disturbance is and has been one of the disability categories specified under the mandatory special education law that has become and been reauthorized as the Individuals With Disabilities Education Act (IDEA) and its implementing regulations (U.S. Department of Education, 2017; Ysseldyke et al., 1982, 1992, 2000). It is currently defined as follows: i. The term means a condition exhibiting one or more of the following characteristics over a long period of time and to a marked degree that adversely affects a child's educational performance: A. An inability to learn that cannot be explained by intellectual, sensory, or health factors. B. An inability to build or maintain satisfactory interpersonal relationships with peers and teachers. C. Inappropriate types of behavior or feelings under normal circumstances. D. A general pervasive mood of unhappiness or depression. E. A tendency to develop physical symptoms or fears associated with personal or school problems. ii. The term includes schizophrenia. The term does not apply to children who are socially maladjusted, unless it is determined that they have an emotional disturbance. (CFR §300.7 (a) 9). Children who meet these criteria, as determined by a multidisciplinary team, may receive services under IDEA.