A child node is an object or element in a tree, or a directed acyclic graph, that resides inside or under another object or element, the parent. It is an element that is immediately subordinate of another element in a file structure arranged in a hierarchical architecture. A child node is also sometimes called a daughter node or a successor node. It is common to say that the child node is a kind of the parent. Things that are associated with child node, a more specialized element, are substitutable for a parent of that particular child node.

A type of organizational structure of classes of elements, databases, or directory files that has this type of generalization or hierarchical structure is called a tree. This type of structure looks like a tree with its different branches and nodes and there is a unique route between any pair of nodes on the tree. The top of the file structure is called the root node and each entry on a different branch is called a child node of the parent. A child node can also be a parent in some cases if it has other objects subordinate to it although there are some objects, such as in an active directory, that can only be child nodes. Also, in any case no child node can have more than one parent.