A mixture in a fluid state (liquid, gas or supercritical fluid).
The mixture components (which are pure substances) in this case are called Fluid Components.
Unlike pure substances the fluid mixtures in a state of Thermodynamic equilibrium may see liquid and gas phases coexist in Vapour Liquid Equilibrium (VLE).
See Also
Natural Science / Chemistry / Chemical Substance / Mixture
[ Pure substance ]
[ Vapour Liquid Equilibrium (VLE) ]