Question

what is degree of freedom in thermodynamics​

Answer 1

So degrees of freedom define physical variables that give a particular system its characteristics. Each degree of freedom lends a particular trait to a system, so giving two examples: ... So degrees of freedom (F) is defined as F = 3 N − 6 for non-linear and F = 3 N − 5 for linear, where N is the number of atoms.

Answer 2

The total number of intensive variables in order to fix the state of the system is called degree of freedom.

As per Gibb's phase rule it states that:

P+F=C+2 ; where P is the number of phases ; C the number of components and F the degree of freedom.

For example: At the triple point of water where all the three phases of water are present that is liquid,gas and solid by Gibb's phase rule the degree of freedom will be ZERO.

PS: the state of the system is the characteristics of the system.