PATH, PATHCONTAINS, PATHITEM, PATHITEMREVERSE, PATHLENGTH – DAX Guide
PATH: Returns a string that contains a delimited list of IDs, starting with the top/root of a hierarchy.
PATHCONTAINS: Returns TRUE if the specified Item exists within the specified Path.
PATHITEM: Returns the nth item in the delimited list produced by the Path function.
PATHITEMREVERSE: Returns the nth item in the delimited list produced by the Path function, counting backwards from the last item in the path.
PATHLENGTH: Returns returns the number of items in a particular path string. This function returns 1 for the path generated for an ID at the top/root of a hierarchy.