In medicine, a persistent and lasting condition is said to be chronic (from Greekchronos). For example, a chronic illness is one that persists for a long time, usually more than three months. By analogy, this adjective has come to describe problems which cannot be solved in a short time, or which will recur regardless of action.
Highly potent cannabisbuds are often referred to as "chronic" or "the chronic" in the official jargon of the American drug trade, while less potent buds and leaves are referred to as "schwag" and "shake", respectively. In the northwestern United States, this term is typically used in reference to BC bud variety of cannabis product. Closely related is the term hydrochronic, a combination of hydroponic and chronic, referring to the buds of highly potent, hydroponically_grown cannabis.
The etymology of the term is simple: "chronic" is often used (colloquially) as a synonym for "intense". Some think it may refer to the potential for addiction generally associated with chronic (i.e. frequent) drug use, but this is unlikely the case, as cannabis is far less addictive than many common consumables such as chocolate or cola drinks.
Slang
From the usage of the term "chronic" in business came the now ubiquitous slang term used among casual stoners. The slang term may refer to any variety of bud, regardless of potency -- with the usual exception of Mexican dirt weed.
Chronic obstructive pulmonary disease (COPD) is an umbrella term for a group of respiratory tract diseases that are characterized by airflow obstruction or limitation.
As the disease continues, the symptoms are seen with increased frequency and severity.
The inflammatory component of the disease can be modified with the use of steroid drugs (usually administered by inhalation in order to avoid any systemic effect) but several weeks of treatment must be given before the effect can be evaluated.