Hxen.com's tips：Every day persisted can learn English well!-->■Learn English Everyday■
concussion – n. an injury to the brain that is caused by something hitting the head very hard
symptom – n. a change in the body or mind which indicates that a disease is present
dizziness – n. the act of being dizzy -- feeling that you are turning around in circles and are going to fall even though you are standing still
anxiety - n. fear or nervousness about what might happen
