connected to connected to in branching relationship with tributary of tributary of This relation can be used for geographic features (e.g. rivers) as well as anatomical structures (veins, arteries) http://en.wikipedia.org/wiki/Tributary tributary channel of tributary_of RO:0002376 http://www.medindia.net/glossary/venous_tributary.htm drains to uberon tributary_of drains into Deschutes River tributary_of Columbia River inferior epigastric vein tributary_of external iliac vein x tributary_of y if and only if x a channel for the flow of a substance into y, where y is larger than x. If x and y are hydrographic features, then y is the main stem of a river, or a lake or bay, but not the sea or ocean. If x and y are anatomical, then y is a vein. http://en.wikipedia.org/wiki/Tributary requires discussion