On $(p,q)$-Appell Polynomials

We introduce polynomial sets of $(p,q)$-Appell type and give some of their characterizations. The algebraic properties of the set of all polynomial sequences of $(p,q)$-Appell type are studied. Next, we give a recurrence relation and a $(p,q)$-difference equation for those polynomials. Finally, some examples of polynomial sequences of $(p,q)$-Appell type are given, particularly, a set of $(p,q)$-Hermite polynomials is given and their three-term recurrence relation and a second order homogeneous $(p,q)$-difference equation are provided.