Name for the "starting vertex" and "ending vertex" of a directed edge Say a graph contains a directed edge e from vertex a to vertex b.  Is there a standard name for vertex a relative to edge e?  And similarly for vertex b?

Something akin to vectors in high school physics, where the initial point of the vector is called the "tail" and the terminal point of the vector is called the "tip"?  I'd like to say something like "a is the tail of edge e" or "b is the terminal vertex of edge e."
$a$ is the tail or initial vertex of the edge $(a,b)$
$b$ is its head or terminal vertex.