In the TCL, the term stored_type is used to refer to the basic type or user defined type (class) which is the type being stored in the tree container. This term is used both in the documentation, to refer to the type being stored in the tree containers, and in the library code. In the code, it is used as the name of the first template parameter for all three tree container classes, as well as the name of the first template parameter for the base tree class.

An element is the term that is given for an object of the type stored_type. So, we say that the tree containers contain nodes, and the nodes contain elements. And elements are of the type stored_type.