birapport bedeutet auf Englisch

cross-ratio▼◼◼◼(a special number associated with an ordered quadruple of collinear points, particularly points on a projective line, and preserved by the fractional linear transformations)
noun
[UK: ˈkrɒs ˈreɪ.ʃɪəʊ] [US: ˈkrɑːs ˈreɪ.ʃiˌo.ʊ]