3. An electronic dictionary as set forth in claim 2, wherein said plural groups of related vocabulary entries each consist of vocabulary entries which are synonymous with each other.
3. An electronic dictionary as set forth in claim 2, wherein said plural groups of related vocabulary entries each consist of vocabulary entries which are synonymous with each other. 6. The electronic dictionary as set forth in claim 3, wherein: said linking data comprises end data which is indicative of each of said plural groups of vocabulary entries; and said group-linking means comprises: start-address memory means for storing first and second start-address data corresponding to the end data for each of said plural groups of vocabulary entries, each of said first start-address data designating the address of the vocabulary entry of the corresponding group stored in said basic-dictionary memory which is first in order of retrieval, and each of said second start-address data designating the address of the vocabulary entry of the corresponding group stored in said at least one expansion-dictionary memory which is first in order of retrieval; and checking and processing means for checking whether the at least one expansion-dictionary memory is installed in which is stored the vocabulary entry designated for next retrieval based on the end data of the retrieved linking data; and (i) if the designated at least one expansion-dictionary memory is not installed, causing said retrieval means to retrieve the vocabulary entry stored in said basic-dictionary memory designated by the first start-address data associated with the retrieved end data; and (ii) if the designated at least one expansion-dictionary memory is installed, causing said retrieval means to retrieve the vocabulary entry stored in the at least one expansion-dictionary memory designated by the second start-address data associated with the retrieved end data.