A drug is a chemical that interacts with other substances to alter or change something. In the United States, drugs are a major part of everyday life. Whenever you have a cup of coffee, drink tea, or flavor something with condiments such as sugar or salt, you are using drugs. In some instances they may be used for positive effects ( aspirin or prescription pain killers in moderation to cure a headache or other sickness). However, sometimes people abuse drugs (alcohol or painkillers) or make use of illegal ones (marijuana, cocaine, ecstasy, LSD ....