Airways
The airways are part of the respiratory (breathing) system; they are the tubes through which air flows to and from the lungs.

Allergens
Allergens are substances that create abnormal reactions in people who are sensitive to (allergic to) them. 

Allergy
If you have an allergy – or are allergic to something – your body reacts abnormally to that thing; it has an "allergic reaction" to it.  There are a variety of allergic reactions; the symptoms of "hay fever,"  including itchy, watery eyes, runny nose, and nasal congestion, are one type of allergic reaction.  The substance(s) you are allergic to are called allergens.

Anti-inflammatory
An anti-inflammatory is a medicine that reduces the swelling (inflammation) of tissues.
Anti-inflammatories used to treat asthma reduce or prevent the swelling in the airways, allowing more air to pass through them and therefore reducing asthma symptoms. 

Asthma
Asthma is a chronic disease that makes breathing difficult. If you have asthma, the inside of your airways react strongly to things you are allergic to (allergens) or find irritating (irritants), causing the airways to narrow so less air can flow through them to the lungs.
Allergens provoke allergic asthma; irritants provoke non-allergic asthma. 

Asthma Attack
An asthma attack is the onset of very severe asthma symptoms.  An asthma attack can make breathing so difficult that emergency treatment is needed.

Asthma Triggers
Asthma triggers are the things that provoke asthma symptoms.

Bronchoconstriction
Bronchoconstriction means the muscles surrounding the airways contract and tighten (constrict), squeezing and narrowing the airways.  Bronchoconstriction is one cause of asthma symptoms.

Bronchodilators
Bronchodilators are medicines that open up the airways by relaxing the muscles that have tightened around them.  They are one of the two kinds of asthma medication; anti-inflammatories are the other.

Histamines
Histamines are chemicals released into the body when the airways are inflamed; they cause the airways to swell, excessive mucous to be produced, and muscles around the airways to contract.  These reactions lead to the symptoms allergies, asthma and an asthma attack. 

Inflammation
Inflammation means tissues or organs have become red and swollen (inflamed).  Inflammation of the airways narrows them, allowing less air to flow through them, and is one cause of asthma symptoms.

Inhaler
An inhaler is a device that delivers asthma medication; a person breathes in through the inhaler to get the medicine.  Various types of inhalers are available; the most common are metered dose inhalers (or MDIs), popularly known as "puffers."
 
Irritants
Irritants are things that irritate the airways of people with non-allergic asthma and provoke asthma symptoms. 

Peak Flow Meter
A peak flow meter is a hand-held device that measures how fast and how much a person can exhale.  It is used to diagnose asthma and to monitor the condition of a person with asthma.

Spriometer  (see Spirometry)

Spirometry
Spirometry is a test for diagnosing asthma that uses a device called a spirometer to measure the amount of air you can breathe and the rate at which it flows through your airways.  It is used to diagnose asthma and to monitor the condition of a person with asthma.