Graphical Representation: Tree (Definitions)

"A complex data structure built from nodes, each of which points to two or more other nodes." (Jesse Liberty, "Sams Teach Yourself C++ in 24 Hours" 3rd Ed., 2001)

"In the hierarchical data mode, a single entity hierarchy." (Jan L Harrington, "Relational Database Design and Implementation" 3rd Ed., 2009)

"A structure for data relationships where all relationships are one-to-many and no child entity may have more than one parent entity." (Jan L Harrington, "SQL Clearly Explained" 3rd Ed., 2010)

"A graph in which child nodes do not have more than one parent. SEE ALSO chart; graph; structure, tree." (DAMA International, "The DAMA Dictionary of Data Management", 2011)

"A hierarchy of things from the same population. The things could be a) instances from a population represented by a single type icon representing the population of instances, and a reflexive relationship on that type, or b) types from the set of types defined in a database represented by a tree structure where each node of the tree is a population of instances of the same type. In the first case, it is the instances that form a tree structure, and in the second, it is the types that form a tree structure. The latter is called a hierarchical data structure." (DAMA International, "The DAMA Dictionary of Data Management", 2011)

"A linked data structure that forms a hierarchy where nodes at higher levels know about a subset of the nodes in the level below them. Each node in a tree can only be reached from a single node in the level above it." (Mark C Lewis, "Introduction to the Art of Programming Using Scala", 2012)

"A structure with a unique starting node (the root), in which each node is capable of having multiple child nodes, and in which a unique path exists from the root to every other node" (Nell Dale et al, "Object-Oriented Data Structures Using Java" 4th Ed., 2016)

"A tree is a constrained graph. Trees are directed graphs because the 'parent of' relationship between nodes is asymmetric: the edges are arrows that point in a certain direction. Trees are acyclic graphs, because if you follow the directed edges from one node to another, you can never encounter the same node twice. Finally, trees have the constraint that every node (except the root) must have exactly one parent." (Robert J Glushko, "The Discipline of Organizing: Professional Edition, 4th Ed", 2016)

"Trees consist of nodes joined by edges, recursively nested. When a single, root dictionary is connected to child nodes that are themselves dictionaries, we say that the dictionaries are nested into a kind of tree structure." (Robert J Glushko, "The Discipline of Organizing: Professional Edition" 4th Ed., 2016)

"Hierarchical data structure where each node may have any number of child nodes, but only one parent node (with the exception of the root node, which has no parent)." (Karl Beecher, "Computational Thinking - A beginner's guide to problem-solving and programming", 2017)