Notations U

$\cup$: union; Common Notations and Definitions
$U(\NVar{x})=\sqrt{\pi}\operatorname{Bi}\left(x\right)$: notation used by Fock (1945); §9.1
(with $\operatorname{Bi}\left(\NVar{z}\right)$ : Airy function and $\pi$ : the ratio of the circumference of a circle to its diameter)
$U_{\NVar{m}}(\NVar{t})$: generalized Airy function; §9.13(i)
$U^{*}_{\NVar{n}}\left(\NVar{x}\right)$: shifted Chebyshev polynomial of the second kind; Table 18.3.1

$\overline{U}\left(\NVar{a},\NVar{x}\right)$: parabolic cylinder function; §12.2(vi)
$\mathsf{U}\left(\NVar{x},\NVar{t}\right)$: Voigt function; (7.19.1)
$U\left(\NVar{a},\NVar{b},\NVar{z}\right)$: Kummer confluent hypergeometric function; (13.2.6)
$\mathit{uE}^{\NVar{m}}_{2\NVar{n}}\left(\NVar{z},\NVar{k^{2}}\right)$: Lamé polynomial; (29.12.1)