Definition for Attention deficit hyperactivity disorder
From Biology Forums Dictionary
1) Attention deficit hyperactivity disorder (ADHD) is a neurodevelopmental psychiatric disorder in which there are significant problems with executive functions (i.e., attentional control and inhibitory control) that cause attention deficits, hyperactivity, or impulsiveness which is not appropriate for a person's age.
2) a learning disability characterized by difficulty in remaining still so that one can concentrate on learning.