Character Usage (Meiji, Taisho & Showa Eras, 1874-1989)
Catalogued headlines and keywords are written in kanji characters designated for everyday use and for personal names in the modern character system. (For example, 山縣有朋 ⇒ 山県有朋、坂本龍馬 ⇒ 坂本竜馬、澁澤榮一 ⇒ 渋沢栄一)
Words and expressions which would not be understood if written using the modern character system -- including common contemporary phrases, historic terms, proper names and the titles of literary works -- are rendered in both modern and archaic forms. (For example, 諮詢・諮問、廓・遊郭、紀事・記事、彙報・雑報)
In the case of characters that are not designated for everyday use or for personal names, the official characters are used. (For example, 桧 ⇒ 檜、祢 ⇒ 禰)
Hiragana characters are used according to modern usage in principle, while some titles of literary works and proper names are expressed in their original form. (For example, 恋のやまひ＝恋の病、かえふ＝かよう＝夏葉、らいてふ＝らいちょう＝雷鳥)
Kanji characters which were used in proper nouns from China, South Korea and North Korea, and are not designated for everyday use or personal names, are replaced by katakana characters. (For example, 浙贛線⇒ 浙カン線、 馬場鍈一 ⇒ 馬場エイ一、 鄧小平⇒ トウ小平)
In addition to these cases, South and North Korean proper nouns are rendered in katakana to give the pronunciation of the original words. (尹潽善 ⇒ 尹フ善＝ユン・ボソン)
Katakana renderings of foreign proper nouns follow modern practice. Some inconsistencies exist in the database for articles up through the end of World War II, reflecting the inconsistent use in the original articles. In these cases, supplementary keywords have been added for the convenience of modern readers. (For example, ローズベルト ⇒ ルーズベルト、墺 ⇒ オーストリア、桑港 ⇒ サンフランシスコ、モスコー ⇒ モスクワ)
To express the pronunciation of the "V ヴ" sound, katakana characters representing the "B バビブベボ" sound are used. The archaic katakana characters which expressed "wi ヰ", "we ヱ", "wo ヲ", "di ヂ", "du ヅ" are replaced by those for "I イ," "e エ," "o オ," "ji ジ," and "zu ズ," respectively, except where they appear in personal names and in the names of particular products (for example, XX ラヂヲ). In some particular product names also, the katakana characters which would be written in small characters in modern usage are rendered in large characters according to their original appearance in advertisements. (For example, フイルム instead of フィルム、ケチヤツプ instead of ケチャップ)
Categorization
Articles are generally divided into categories and regions corresponding to modern usage. In exceptional cases where these have greatly altered since the time of publication, however, some articles may be categorized on the basis of regional demarcations at the time of publication.