(chemistry) any group of elements whose chemical and physical properties have similarities, and that vary progressively through the series; evident within the periodic table

Any noxious substance intended for use in military or police operations.

plural of chemical element

(geology) the chemical boundary layer between the surface of the Earth and the asthenosphere that contains the material differentiated or extracted from the mantle

The system for naming chemical compounds. There are two systems of chemical nomenclature:

(chemistry) any process in which reactants are changed into products by the breaking or creation of chemical bonds

(chemistry) Any mixture of compounds whose relative concentrations oscillate, and in which such change is marked by a visible rhythmic change in colour.

A medical treatment using a anaphrodisiacal hormonal drug to inhibit the function of a man's testes, intended to have the same effect on the sex drive as surgical castration. It is typically used on sex offenders as a punishment and/or preventative measure, or on people wishing to undergo male-to-female transsexualism.

any cosmetic preparation designed to remove hair from the skin

(chemistry) any substance used to classify another, often by changing colour