Approximate string matching of a target string to a trie data structure. The trie data structure has a root node and generations of child nodes each node representing at least one character in an alphabet to provide a lexicon of words and word fragments. The trie data structure is traversed starting from the root node by comparing each node of a branch of the trie data structure to characters in the target string and adding characters traversed in a branch of the trie data structure to a gathered string to provide suggestions of approximate matches. If a node is reached that is flagged as a node for a word or a word fragment and, if the target string is longer than the gathered string, the traversal loops back to the root node, and continues to traverse from the root node. This enables the trie data structure to use word fragments for compound words and to split non-delimited words where appropriate. A determination may be made, at each node, as to whether there is a correction rule for one or more characters in the remainder of the target string from the current node, and if so, the correction rule is applied to the target string to obtain a modified target string.