Professionally speaking, they are both Attention-Deficit/Hyperactivity Disorder and many people use the terms ADD and ADHD interchangeably. However, there is a difference for practical and clinical purposes. Attention Deficit Hyperactivity Disorder is broken down into three classes based on the symptoms of the individual:

• Hyperactive-Impulsive Type — includes symptoms of hyperactivity and impulsivity but without inattention.
• Inattentive Type — includes symptoms of inattention but the symptoms of hyperactivity and impulsivity are absent.
• Combined Type —includes symptoms of both inattention and hyperactivity-impulsivity.

Based on these classifications, Attention Deficit Disorder (ADD) is considered to be the inattentive type, where inattention symptoms are present but hyperactive and impulsive behaviors are not. Attention Deficit Hyperactivity Disorder (ADHD) describes the other two classifications where hyperactivity and impulsivity symptoms are present.