Uses
The Nikkoku, because of its size, has many features normally found only in specialized dictionaries. These include: definitions and etymologies of foreign loan words (gairaigo, 外来語), highly recent words (gendai yōgo, 現代用語), archaic words (kogo, 古語), idiomatic compound phrases (jukugo, 熟語), words that can be written using more than one possible Chinese character to produce subtle differences in meaning (dōkun iji, 同訓異字), and Chinese characters that are written differently but have the same pronunciation (iji dōkun, 異字同訓), some slang (ingo, 隠語), and words used only in regional dialects (hōgen, 方言). Certain specialized dictionaries may have a few entries that do not exist in the Nikkoku, and many specialized scholars will need to rely on specialized dictionaries, but it is certainly sufficient for most general reference needs.
Read more about this topic: Nihon Kokugo Daijiten