 More specifically, directed graphs without loops are addressed as simple directed graphs, while directed graphs with loops are addressed as "loop-digraphs" (see section Types of directed graphs).An arrow is considered to be directed "from" "x" "to" "y"; "y" is called the "head" and "x" is called the "tail" of the arrow; "y" is said to be a "direct successor" of "x" and "x" is said to be a "direct predecessor" of "y".If a path leads from "x" to "y", then "y" is said to be a "successor" of "x" and "reachable" from "x", and "x" is said to be a "predecessor" of "y".