nicotine

Alkaloid (nitrogenous compound) obtained from the dried leaves of the tobacco plant Nicotiana tabacum. A colourless oil, soluble in water, it turns brown on exposure to the air. Nicotine is found in tobacco smoke. It can be described as a recreational drug. It stimulates the human body and produces feelings that cause people to carry on smoking. However, nicotine is usually addictive (see addiction). Regular smokers find that it is very difficult or impossible to give up smoking even though they may try to. This is a problem, in that other chemicals in smoke cause a wide range of diseases and increase the risk of dying early. Nicotine has also been used as an insecticide.

Nicotine in its pure form is one of the most powerful poisons known. It is named after a 16th-century French diplomat, Jacques Nicot, who introduced tobacco to France.