The molar heat capacity of a gas in a process

For the polytropic process P$V^n$ molar specific heat is given by   c = $\frac{(\gamma -n)}{(1-n)}{C}_v$

When n$>\gamma , C is positive$

When n$<1, C is positive.$

When $\gamma >n>1, C is negative$

When n =1, C is infinity

When n=$0$,C is zero

In other words, C can have any real value, depending upon the type of thermodynamics process.