Principal Vertex

A Vertex $x_i$ of a Simple Polygon $P$ is a principal Vertex if the diagonal $[x_{i-1}, x_{i+1}]$ intersects the boundary of $P$ only at $x_{i-1}$ and $x_{i+1}$.

See also Ear, Mouth

References

Meisters, G. H. ``Polygons Have Ears.'' Amer. Math. Monthly 82, 648-751, 1975.

Meisters, G. H. ``Principal Vertices, Exposed Points, and Ears.'' Amer. Math. Monthly 87, 284-285, 1980.

Toussaint, G. ``Anthropomorphic Polygons.'' Amer. Math. Monthly 98, 31-35, 1991.