Assertion: polygon | /r/HasProperty | concave
Facets:
Source sentences:
text: The polygon must be simple, and may be convex or concave.
text: Polygons can be convex, concave, or star.
text: Notice that this definition allows polygons to be either concave or convex.
text: A polygon (which has straight sides) is concave when there are "dents" or indentations in it (where the internal angle is greater than 180°)