Atom: A unit of matter, the smallest unit of an element, having all the characteristics of that element. Consists of a dense, central, positively charged nucleus that is surrounded by a system of electrons.

Molecule: A group of like or different atoms held together by chemical forces.

Bond: A force of attraction by which atoms or ions are bound in a molecule or crystal

Polymer: Natural and man-made compounds of usually high molecular weight consisting of up to millions of repeated linked units, each a relatively light and simple molecule