'Apnea' (AP-nee-uh) comes from the Greek word meaning 'want of breath,' and it refers to an abnormal, temporary stopping of breathing. It's most common form is sleep apnea, a breathing disorder first described in 1965 that's characterized by brief interruptions of breathing during sleep.

Asthma is a chronic disease marked by periodic attacks of wheezing and difficulty breathing, especially exhaling. During an asthma attack, the air passages in the lungs become narrow or blocked by mucus or a muscle spasm.

There are two types of bronchitis: acute and chronic. Acute bronchitis is the inflammation of the mucous membrane that lines the bronchi (BRAWNK-eye), or main passages of the lungs, and usually only lasts a few days.

Emphysema (em-fa-SEE-ma) is a chronic, irreversible lung disease that slowly destroys the air sacs in the lungs. This reduces the elasticity of the lungs and interferes with breathing, making it hard to move air in and out of the lungs.