A substance formed from two or more atoms that unite (bond) in a fixed proportion and structure. The properties of materials that are the result of various reactions between different compounds.

A part of an experiment where there is no change from normal conditions. Essential to scientific experiments. It shows that any new effect is likely due only to the part of the test that a researcher has altered.

A type of mental disorder caused by disease or injury that causes people to gradually lose all or part of their memory. It may start out temporary and build to a permanent condition where the ability to reason also is impaired.

Battery-powered device that disperses nicotine and other chemicals as tiny airborne particles that users can inhale. They were originally developed as a safer alternative to cigarettes that users could use as they tried to slowly break their addiction to the nicotine in tobacco products. These devices heat up a flavored liquid until it evaporates, producing vapors. People use these devices are known as vapers.

A molecule (typically highly reactive and short-lived) having one or more unpaired outer electrons. It will attempt to steal electrons to make itself whole again through a process known as oxidation.

Able to ward off a particular infection. Alternatively, this term can be used to mean an organism shows no impacts from exposure to a particular poison or process. More generally, the term may signal that something cannot be hurt by a particular drug, disease or chemical.

A colorless, oily chemical produced in tobacco and certain other plants. It creates the “buzz” associated with smoking. Highly addictive, it is the substance that makes it hard for smokers to give up their use of cigarettes. The chemical is also a poison, sometimes used as a pesticide to kill insects and even some invasive snakes or frogs.

A condition where more oxidative chemicals are being formed or affecting cells than can be managed by the body’s antioxidant defense system. Some diseases or injuries increase the production of free radicals, leading to tissue damage.

A field of medicine that has to do with children and especially child health. A doctor who works in this field is known as a pediatrician.

Too early; before something should occur.

A compound made from one or more long chains of amino acids. They are an essential part of all living organisms and form the basis of living cells, muscles and tissues; they also do the work inside of cells.

A mental, physical, emotional or behavioral reaction to an event or circumstance that disturbs a person or animal’s usual state of being or places increased demands on a person or animal; psychological stress can be either positive or negative.

New member of a group or human trial. To enroll a new member into a research trial. Some may receive money or other compensation for their participation, particularly if they enter the trial healthy.

a result or effect of an action or condition