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  "body": "\n## Summary\n\nThe Bloch–Wigner function $D$ is a real-valued function on the complex plane built from the imaginary part of the [[dilogarithm|G0X0NWSDB7]] and a logarithm correction.\nUnlike the dilogarithm, it is single-valued and continuous on all of $\\C$.\nIt satisfies a clean five-term relation and gives the volume of an ideal tetrahedron in hyperbolic space.\nThis makes it central in hyperbolic geometry and in the theory of the Bloch group.\n\n## Explanations\n\n### L1 human\n\nThe dilogarithm is a multivalued function: going around the point $1$ changes its value.\nThe Bloch–Wigner function takes the imaginary part and adds just the right correction so that these jumps cancel.\nThe result is a smooth real function on the plane with the points $0$ and $1$ removed, and it extends continuously to them with value $0$.\nIt is zero on the real line and changes sign under complex conjugation.\nIts largest value, about $1.0149$, is reached at $z = e^{i\\pi/3}$, and this number is the volume of the regular ideal tetrahedron in hyperbolic space.\n",
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