Solid has two forms:
1. Crystalline: The atoms of crystalline solids have a definite three-dimensional arrangement. They are anisotropic, symmetrical, rigid, and have a sharp melting point. They are considered true solids.
2. Amorphous: The atoms of amorphous solids do not have a definite arrangement. They are isotropic, asymmetrical, less rigid, and do not have sharp melting points. They are also referred to as pseudo solids.