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.
A list and molar fractions of all fluid components constituting a fluid mixture is called Fluid Composition.
Unlike pure substances the fluid mixtures in a state of Thermodynamic equilibrium may see liquid and gas phases occupy a continuous area in PT Diagram (see also Vapour Liquid Equilibrium).
The mass fraction of liquid and gas phases is also called Liquid Quality and Vapour Quality correspondingly.
See Also
Natural Science / Chemistry / Chemical Substance / Mixture
[ Pure substance ][ Liquid Quality ]][ Vapour Quality ]
[ Vapour Liquid Equilibrium (VLE) ]