States of the matter
The three states of matter are described as solid, liquid and gas.
The condensed states, e.g. liquids and solids, are incompressible. The fluid states, e.g. liquids and gases do not have a distinct shape but adopt that of the vessel which contains them. A plasma is sometimes regarded as a particular state of the matter.
System of state
A system of state corresponds to all the parameters which make it possible to characterize the properties of a system. In chemistry, the system of state of a system is defined as the sum of the physical parameters (temperature, pressure) and chemical parameters (composition) which characterize it.