STATE 

The State of a system is its condition or configuration described in sufficient detail. State is the condition of the system identified by thermodynamic properties such as pressure, volume, temperature, etc. The number of properties required to describe a system depends upon the nature of the system. However each property has a single value at each state. Each state can be represented by a point on a graph with any two properties as coordinates. 

Any operation in which one or more of properties of a system change is called a change of state. 

Point Function

 A point function is a single valued function that always possesses a single – value is all states. For example each of the thermodynamics properties has a single – value in equilibrium and other states. These properties are called point function or state function.

 Or

 when two properties locate a point on the graph ( coordinates axes) then those properties are called as point function.

 For example pressure, volume, temperature, entropy, enthalpy, internal energy. 

Path Function

Those properties, which cannot be located on a graph by a point but are given by the area or show on the graph.

A path function is different from a point function. It depends on the nature of the process that can follow different paths between the same states. For example work, heat, heat transfer.