when we say that trees are "nonlinear,we are referring to an organizational relationship that is richer than the simple "beforeand "afterrelationships between objects in sequences the relationships in tree are hierarchicalwith some objects being "aboveand some "belowothers actuallythe main terminology for tree data structures comes from family treeswith the terms "parent,"child,"ancestor,and "descendentbeing the most common words used to describe relationships we show an example of family tree in figure figure family tree showing some descendents of abrahamas recorded in genesis - tree definitions and properties tree is an abstract data type that stores elements hierarchically with the exception of the top elementeach element in tree has parent element and zero or more children elements tree is usually visualized by placing elements inside ovals or rectanglesand by drawing the connections between parents and children with straight lines (see figure we typically call the top element the root of the treebut it is drawn as the highest elementwith the other elements being connected below (just the opposite of botanical treefigure tree with nodes representing the organization of fictitious corporation the root stores