DLMF: Notations I

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$\mathbf{I}$: unit matrix; Common Notations and Definitions
$I^{{\alpha}}$: fractional integral; (2.6.33)
$I^{{\alpha}}$: fractional integral; (1.15.47)
$I(\mathbf{m})$: general elliptic integral; §19.29(ii)
$\imagpart{}$: imaginary part; (1.9.2)
$\mathop{I_{{\nu}}\/}\nolimits\!\left(z\right)$: modified Bessel function; (10.25.2)
$\mathop{\widetilde{I}_{{\nu}}\/}\nolimits\!\left(x\right)$: modified Bessel function of imaginary order; (10.45.2)
$\mathop{{\mathsf{i}^{{(1)}}_{{n}}}\/}\nolimits\!\left(z\right)$: modified spherical Bessel function; (10.47.7)
$\mathop{{\mathsf{i}^{{(2)}}_{{n}}}\/}\nolimits\!\left(z\right)$: modified spherical Bessel function; (10.47.8)
$\mathop{I_{{x}}\/}\nolimits\!\left(a,b\right)$: incomplete beta function; (8.17.2)
$I(a,b,x)=\mathop{I_{{x}}\/}\nolimits\!\left(a,b\right)$: notation used by Magnus et al. (1966); §8.1
(with $\mathop{I_{{x}}\/}\nolimits\!\left(a,b\right)$ : incomplete beta function)

$\mathop{\mathrm{idem}\/}\nolimits\!\left(\chi _{1};\chi _{2},\dots,\chi _{n}\right)$: $\mathop{\mathrm{idem}\/}\nolimits$ function; §17.1
$\mathop{\mathrm{Ie}_{{n}}\/}\nolimits\!\left(z,h\right)$: modified Mathieu function; (28.20.17)
$\mathop{\mathrm{i}^{{n}}\mathrm{erfc}\/}\nolimits\!\left(z\right)$: repeated integrals of the complementary error function; (7.18.2)
$\mathrm{in}_{n}(z,q)=\mathop{\mathrm{fe}_{{n}}\/}\nolimits\!\left(z,q\right)$: notation used by Campbell (1955); ¶ ‣ §28.1
(with $\mathop{\mathrm{fe}_{{n}}\/}\nolimits\!\left(z,q\right)$ : second solution, Mathieu’s equation)
$\inf$: greatest lower bound (infimum); Common Notations and Definitions
$\mathrm{inh}_{n}(z,q)=\mathop{\mathrm{Fe}_{{n}}\/}\nolimits\!\left(z,q\right)$: notation used by Campbell (1955); ¶ ‣ §28.1
(with $\mathop{\mathrm{Fe}_{{n}}\/}\nolimits\!\left(z,q\right)$ : modified Mathieu function)
$\mathrm{inv}$: inversion number; §26.14(i)
$\mathop{\mathrm{inverf}\/}\nolimits x$: inverse error function; (7.17.1)
$\mathop{\mathrm{inverfc}\/}\nolimits x$: inverse complementary error function; (7.17.1)
$\mathop{\mathrm{Io}_{{n}}\/}\nolimits\!\left(z,h\right)$: modified Mathieu function; (28.20.18)