Which property distinguishes solids from liquids?

The distinguishing property of solids that differentiates them from liquids is their fixed shape and volume. Solids maintain their shape and do not conform to the shape of their container, which is a fundamental characteristic of solids. Unlike liquids, which take the shape of the container they are in while maintaining a fixed volume, solids have a rigid structure that keeps them from flowing. This rigidity is due to the close packing of particles in solids, leading to strong intermolecular forces that hold the particles in specific positions.

In addition to shape and volume, the other properties listed do not help differentiate solids from liquids in the same fundamental way. Liquids can flow (which denotes their adaptability in shape), have a fixed volume but not a fixed shape, are generally less compressible than gases but more so than solids, and the ability to conduct electricity is not exclusive to either state of matter—some solids are conductors, and some liquids can conduct electricity as well.