Vertex centroid
= Vertex centroid
{title2=$c=\frac1n\sum_{j=0}^{n-1}v_j$}
The arithmetic mean of a finite nonempty collection of <vertices>, treating each vertex as an equal point mass. For a <polygon>, this need not equal the uniform-area <centroid> of its interior. A <translation> or <linear map> commutes with this average; consequently rotating all vertices about their vertex centroid leaves that centroid fixed.