The Japanese writing system primarily uses kanji, characters (logograms) of Chinese origin. In many important cases, a word in kanji may have both an on-yomi (Sino-Japanese) reading and a kun-yomi (native Japanese) reading.Name of Japan
Since the seventh century AD the name of the polity has been written in kanji with the on-yomi reading Nippon or Nihon (Chinese: Rìběn). The distinction between the two readings - both in current use - depends on the historic and cultural context, as well as on the level of solemnity.
The earliest evidence for the official use of this name for the Japanese polity occurs in a message to the ruler of the Suí imperial state (China) in AD 607.
The same characters have been used to yield the kun-yomi reading Yamato; this reading, usually with different characters, applies more specifically to (the province conceived as) the "heartland" of the early Japanese state, but is also in use as a name for the entire polity. The usual on-yomi reading Nippon Koku for "State of Japan" can be given the kun-yomi reading Yamato-no-kuni.Style of the ruler
The style tennō (on-yomi reading; Chinese: tiānhuáng, meaning "heavenly sovereign") for the ruler of Japan came into use ca AD 672 and has remained the essential official style. The Chinese style tiānhuáng - also documented as in very brief use by rulers of the Táng imperial state (China) - alludes to the Polar Star and the axis mundi embodied by the holder of the imperial office. The process and timing of the adoption of the style tennō is fully discussed in [Williams, pp. 21-22].
Earlier rulers are described by historians as using the style ōkimi (Chinese: dàwáng, meaning "great king"). The term sumera-mikoto, part of the old posthumous names of the rulers (v.i.), is held to be a kun-yomi reading of the characters reading tennō.
It is generally asserted that tennō is a style exclusive to the ruler of Japan and is used without qualification; a ruler of another polity (e.g., China) of the same perceived rank being referred to as kōtei (Chinese: huángdì).The absence of qualification does, however, have official exceptions: in some documents issued in mid-twentieth century the style of the ruler is found printed as Dai Nippon Teikoku Tennō ("Sovereign of the Great Japan Empire"). Some earlier documents of the same century use Nippon Koku Kōtei.Names of the Ruler
This record shows the following:
(a) Personal name. This is usually conferred on a prince or princess at maturity and is tabooed after the accession of a ruler.
(b) Palace name. People in a position of authority, including the rulers, were often called by the location they were born in or lived in. Starting with Okiko (ruled 1629-1643), most of the rulers bore a palace name of the form xxx-no-miya conferred at, or immediately after birth, and not retained at accession.
(c) Posthumous name (okurina) The posthumous name by which each ruler has become officially identified and is systematically recorded in history was introduced ca. AD 672 and was retroactively assigned to all earlier rulers. It consists of a "motto", followed by the word tennō. It is adopted after the ruler's death: in the later and modern practice, immediately after death; but in 1870 posthumous names were adopted for a few rulers who only at that date were officially recognized as having reigned.
As noted in [Williams], in very early times, notably in the period covered by the Nihon-shoki chronicle [Nihongi], a kun-yomi posthumous name, called wafū shigō by historians (with reference to the historically fraught name Wa for the polity), is recorded as having been assigned immediately after death. In this record it is termed "old posthumous name". This name was superseded later in the record by the now usual posthumous name, referred to, in contrast, as kanpū shigō, i.e., "Chinese name".
(d) Era name. An era name (nengō) is the official slogan, usually of good omen, declared and applied for a period of years, and used in dating; it was changed as circumstances dictated (since 1868 it is coterminous with a reign).
In imitation of Chinese practice, the use of nengō (Chinese: niánhào) was tentatively introduced in AD 645 and then suspended; after the occasional use of a "private era name" (shi-nengō), the use of an era name (nengō) was resumed in AD 701 and has remained in permanent use to this day.Southern and Northern Courts period (Nanboku-chō jidai) (1331-1392)
The present account follows the official understanding of the period, confirmed by the Decree of 3 Mar 1911 (Meiji 44) according to which the rulers of the Southern Court (Nan-chō) are recognized as constituting the legitimate succession.