I have used the notion of a directed graph which has at most one path between any two nodes (examples: trees, complete bipartite graph) in a research paper on a topic only tangentially related to graph theory. Is there a name for a graph having this property?
Example: [(1, 2), (2, 3)] (a line) but not [(1, 2), (2, 3), (1, 3)] since there would then be two paths from 1 to 3.