This study is about degenerate Hermite Appell polynomials in three variables
or ?h-Hermite Appell polynomials which include both discrete and degenerate
cases. After we recall the definition of these polynomials and special
cases, we investigate some properties of them such as recurrence relation,
lowering operators (LO), raising operators (RO), difference equation (DE),
integro-difference equation (IDE) and partial difference equation (PDE).We
also obtain the explicit expression in terms of the Stirling numbers of the
first kind. Moreover, we introduce 3D- ?h-Hermite ?-Charlier polynomials,
3D-?h-Hermite degenerate Apostol-Bernoulli polynomials, 3D-?h-Hermite
degenerate Apostol-Euler polynomials and 3D-?h-Hermite ?-Boole polynomials
as special cases of ?h-Hermite Appell polynomials. Furthermore, wederive the
explicit representation, determinantal form, recurrence relation, LO, RO and
DE for these special cases. Finally, we introduce new approximating
operators based on h-Hermite polynomials in three variables and examine the
weighted Korovkin theorem. The error of approximation is also calculated in
terms of the modulus of continuity and Peetre?s K-functional