300px|thumb|A tree structure showing the possible hierarchical organization of an encyclopedia 300px|thumb|The original Encyclopédie (1752) used a tree diagram to show the way in which its subjects were ordered. A tree structure, tree diagram, or tree model is a way of representing the hierarchical nature of a structure in a graphical form. It is named a "tree structure" because the classic representation resembles a tree, although the chart is generally upside down compared to a biological tree, with the "stem" at the top and the "leaves" at the bottom.
300px|thumb|a tree structure showing the possible hierarchical organization of an encyclopedia 300px|thumb|the original encyclopédie (1752) used a tree diagram to show the way in which its subjects were ordered a tree structure tree diagram or tree model is a way of representing the hierarchical nature of a structure in a graphical form it is named a "tree structure" because the classic representation resembles a tree although the chart is generally upside down compared to a biological tree with the "stem" at the top and the "leaves" at the bottom