6. The conversational sentence translation apparatus according to claim 1, wherein the semantic feature dictionary includes a variable semantic feature dictionary in which information on variable semantic features is stored, each variable semantic feature being such a semantic feature that its corresponding character string is replaceable with another character string, said information on each variable semantic feature including a name of the variable semantic feature, one or more entry names of the variable semantic feature, one or more character strings in the first language for each entry name which are elements of sentences in the first language, and a translation in the second language of each entry name; in the bilingual database, variable semantic feature information for specifying a variable semantic feature is annexed to each conversational sentence example and its translation and the semantic feature string for the conversational sentence example, respectively; said apparatus further comprises a feature element replacer for, with reference to the variable semantic feature dictionary and the variable semantic feature information, replacing character strings corresponding to a variable semantic feature in the conversational sentence example selected by the semantic searcher and its translation with an entry name of a variable semantic feature in the input conversational sentence and a translation in the second language of the entry name, respectively.
6. The conversational sentence translation apparatus according to claim 1, wherein the semantic feature dictionary includes a variable semantic feature dictionary in which information on variable semantic features is stored, each variable semantic feature being such a semantic feature that its corresponding character string is replaceable with another character string, said information on each variable semantic feature including a name of the variable semantic feature, one or more entry names of the variable semantic feature, one or more character strings in the first language for each entry name which are elements of sentences in the first language, and a translation in the second language of each entry name; in the bilingual database, variable semantic feature information for specifying a variable semantic feature is annexed to each conversational sentence example and its translation and the semantic feature string for the conversational sentence example, respectively; said apparatus further comprises a feature element replacer for, with reference to the variable semantic feature dictionary and the variable semantic feature information, replacing character strings corresponding to a variable semantic feature in the conversational sentence example selected by the semantic searcher and its translation with an entry name of a variable semantic feature in the input conversational sentence and a translation in the second language of the entry name, respectively. 11. The conversational sentence translation apparatus according to claim 6, wherein said feature element replacer comprises: a character string detecting means for, with reference to the semantic features extracted by the analyzer, detecting a character string corresponding to a variable semantic feature that is a replacement object in the input conversational sentence; and a coincidence deciding means for, with reference to the semantic features extracted from the input conversational sentence by the analyzer and the variable semantic feature information, deciding whether or not a semantic feature present at a specified position relative to the replacement-object variable semantic feature in the conversational sentence example selected by the semantic searcher is coincident with a semantic feature present at the specified position relative to the character string detected by the character string detecting means in the input conversational sentence, and for, if the decision result is a non-coincidence, making the character string detecting means detect another character string, wherein if the decision result by the coincidence deciding means is a coincidence, then the feature element replacer replaces the character string corresponding to the replacement-object variable semantic feature in the selected conversational sentence example and in the translation thereof with a variable semantic feature entry name corresponding to the character string detected by the character string detecting means and a translation of the variable semantic feature entry-name, respectively.