**6. Conclusions**

It has been shown that the first and second kind Chebyshev polynomials play an important role in separating the even part from the odd part of several polynomials and special functions, which include the Appell polynomials, the first kind Bessel functions and the recently introduced Appell–Bessel functions [2]. This is another remarkable property of Chebyshev's classic polynomials within Function theory, which seems to be the counterpart of another, highlighted in [1], which showed its role in separating the real from the imaginary part of Appell's polynomials.

**Author Contributions:** Review and editing, P.N.; investigation, original draft preparation, P.E.R.

**Funding:** This research received no external funding.

**Conflicts of Interest:** The authors declare that they have not received funds from any institution and that they have no conflict of interest.
