3. The navigation device according to claim 1 , wherein said navigation device further includes a gesture recognizer that recognizes a gesture, and said route guidance expression interpreter interprets the route guidance expression extracted by said route guidance expression extractor on a basis of a result of the recognition by said gesture recognizer to determine the concrete route guidance expression.
4. The navigation device according to claim 3 , wherein said navigation device further includes a contradiction determinator that determines whether or not there is a contradiction between the route guidance expression extracted by said route guidance expression extractor and the recognition result obtained by said gesture recognizer, and, when said contradiction determinator determines that there is a contradiction between them, said route guidance expression interpreter selects either one of the route guidance expression extracted by said route guidance expression extractor and the recognition result obtained by said gesture recognizer according to a predetermined rule to determine said concrete route guidance expression.