What are a parent and a child (parent / child)?

In a tree, the terms parent and child describe the hierarchical relationships between nodes.

Parent:

• a node from which an edge goes out to another node;
• every node (except the root) has exactly one parent.

Child:

• a node that is connected to a parent through an edge and sits one level lower;
• a node can have several children (0, 1, 2, ...).

Example:

• A is the parent of B and C.
• B is the parent of D and E.
• D and E are children of B.
• B and C are children of A.

Summary: A parent is a node higher up in the hierarchy, a child is a node lower down, connected to it through an edge.