Number of projective equivalence classes of irreducible linear representations

Definition
Suppose $$G$$ is a finite group and $$K$$ is a field. The number of projective equivalence classes of irreducible linear representations is defined in the following equivalent ways:


 * It is the number of equivalence classes of irreducible linear representations of $$G$$ over $$K$$ under the action of the multiplicative group of one-dimensional representations.
 * It is the number of equivalence classes of irreducible linear representations under the equivalence relation of being projectively equivalent (see also projective representation).