| context | $p\in \mathbb N$ |
| definiendum | $\lambda^p\equiv\eta^p|_{\mathfrak{L}^p}$ |
$\lambda^p:\mathfrak{L}^p\to \overline{\mathbb{R}}$ is the restriction of Lebesgue outer measure to a domain which contains only actually measurable sets.
Wikipedia: Lebesgue measure