molecule

The smallest particle of a substance that retains the chemical and physical properties of the substance and is composed of two or more atoms; a group of like or different atoms held together by chemical forces.

A small particle; a tiny bit.

The smallest mass of any substance which is capable of existing in a separate form — that is, the smallest part into which the substance can be divided without destroying its chemical character (identity).

A very small particle or bit of something; a particle; an atom.

In ornithology, the tread or cicatricula of a fecundated ovum.