An amorphism, in chemistry, crystallography and, by extension, to other areas of the natural sciences is a substance or feature that lacks an ordered form.
In the specific case of crystallography, an amorphic material is one that lacks long range (significant) crystalline order at the molecular level.
In the history of chemistry, amorphism was recognised even before the discovery of the nature of the exact atomic crystalline lattice structure.
In the context of solids, amorphous and crystalline are terms used to describe the structure of materials.
The atoms or molecules in amorphous substances are arranged randomly without any long-range order.