| A | B |
|---|
| activity level | The amount of sheer physical movement that a child engages in per unit of time. |
| allergens | Specific substances, such as pollens and environmental tobacco smoke, that may trigger allergic reactions among individuals who are allergic to them. |
| ambidextrous | Lack of preference for right or left hand; ability to use either hand equally well. |
| asthma | A condition that impairs breathing due to narrowing and inflammation of the air passageways triggered by allergens or other environmental substances. |
| booster seat | A type of safety seat used in a motor vehicle to restrain children who weigh 40–80 pounds. |
| enuresis | Bed-wetting, which is linked to genetic factors and which usually disappears without special treatment as children grow older. |
| environmental tobacco smoke | Smoke from cigarettes and other tobacco products that exists in the environments of smokers; often called secondhand smoke. |
| fine motor skills | Motor skills that involve the use of small muscles; examples are fastening buttons and eating with a spoon. |
| food intolerance | A negative reaction to specific foods. |
| gross motor skills | Motor skills that use the large muscles; examples are running and jumping. |
| handedness | The preference that most people show for completing skilled actions with one hand rather than the other. |
| hemispheres | In the human brain, the term for the two halves of the cerebral cortex, because they look like "half-spheres." |
| myelination | The process through which neural axons become coated with a fatty sheath of myelin, providing insulation and enabling rapid transmission of neural impulses. |
| neurotoxins | Chemical substances that are harmful to children's developing nervous systems, such as lead and mercury. |
| night terrors | Physical thrashing and vocal distress, which do not awaken the child from sleep; almost never recalled by the child; usually occur in the hour or two after falling asleep. |
| nightmares | Frightening dreams that usually happen in the latter half of the night and that may awaken the child from sleep; often recalled by the child in the morning. |
| obesity | An overweight condition defined as people who weigh at least 30% more than the ideal weight for their height and age; in early childhood, those weighing more than 95% of children of the same age and gender. |
| ozone | A highly reactive form of oxygen that results primarily from the action of sunlight on hydrocarbons emitted in fuel combustion (e.g., from cars); a principal component of outdoor air pollution, or smog. |
| parasomnias | Minor sleep disturbances such as walking and talking while still asleep; usually disappear without special intervention as children grow older. |
