a collection of items organized hierarchically where, if we assume the root is at level 0, a node at level is associated with the i-th character of the key. The branching ratio is high, and efficient lookup of words is possible if compression of the data structure does not unduly slow search.

a data structure similar to but different to a tree

a data structure that stores an associative array with string-valued keys

a digital search tree in which leaves correspond to records in a file