Midpoint
= Midpoint
{title2=$m=(a+b)/2$}
{wiki}
The midpoint of the <line segment> joining two points with position vectors $a,b$ is the point $m=(a+b)/2$. Its displacements from the endpoints are $(b-a)/2$ and $(a-b)/2$, so it lies on the segment and is equidistant from its endpoints. It is also the <centroid> of the two endpoints.