(chemistry) Any one of the simplest chemical substances that cannot be decomposed in a chemical reaction. Chemical elements consist of atoms which have the same number of protons.

(chemistry, physics) The science that studies chemical processes and phenomena from the point of view of physics.

(chemistry) a symbolic representation of a chemical reaction; reactants are represented on the left, and products on the right

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

(chemistry) the set of all possible stable molecules

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

A medical, rather than surgical, abortion induced by a drug.

(chemistry) All the various attractions between elements and compounds that lead to their reaction.

(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.