A 
drug, broadly speaking, is any substance that, when absorbed into the body of a living organism, alters normal bodily function.[SUP]
[3][/SUP] There is no single, precise definition, as there are different meanings in 
drug control law, 
government regulations, 
medicine, and colloquial usage.[SUP]
[4][/SUP]
 In 
pharmacology, a drug is "a 
chemical  substance used in the treatment, cure, prevention, or diagnosis of  disease or used to otherwise enhance physical or mental well-being."[SUP]
[4][/SUP] Drugs may be prescribed for a limited duration, or on a regular basis for 
chronic disorders.[SUP]
[5][/SUP]
 
Recreational drugs are chemical substances that affect the 
central nervous system, such as 
opioids or 
hallucinogens.[SUP]
[5][/SUP] They may be used for perceived beneficial effects on 
perception, 
consciousness, 
personality, and 
behavior.[SUP]
[5][/SUP][SUP]
[6][/SUP] Some drugs can cause 
addiction and/or habituation.[SUP]
[6][/SUP]
 Drugs are usually distinguished from 
endogenous biochemicals by being introduced from outside the organism.[SUP][
citation needed][/SUP] For example, 
insulin  is a hormone that is synthesized in the body; it is called a hormone  when it is synthesized by the pancreas inside the body, but if it is  introduced into the body from outside, it is called a drug.[SUP][
citation needed][/SUP] Many natural substances, such as 
beers, 
wines, and 
psychoactive mushrooms, blur the line between food and recreational drugs, as when ingested they affect the functioning of both 
mind and 
body  and some substances normally considered drugs such as DMT  (Dimethyltryptamine) are actually produced by the human body in trace  amounts.