The Empress (皇后)

Empress is the wife of the emperor. Under the polygamy system, empress is the legally wedded wife of the emperor, out of the multiple wives.

Ranks of empress in Japan

According to 'Kojiki' (The Records of Ancient Matters) and 'Nihon Shoki,' (Chronicles of Japan) wives and concubines of Okimi (Yamato sovereignty) were called 'Kisaki' out of which the one with the highest rank was distinguished from the rest of the wives and concubines that were simply called 'Kisaki', and was called 'Ohkisaki.'
In 'Kojiki,' the Kanji '大后' and in 'Nihon Shoki,' the Kanji '皇后' are assigned. There are many articles of genealogy in 'Kojiki' and 'Nihon Shoki' that were created and it is possible that 'Okisaki' who do not have 'konintan' (tales of marriages) with the 'Okimi' were actually sisters. There is a theory that says 'Kisaki' originally meant '君幸' but its origin is not known clearly.

In later years, 'Kisaki' started to mean empress and the empress was also called 'Kisai no miya.'
Based on this, Imperial Princes and Princesses, who had the empress as the mother, are called kisaibara. They were either known by another name (Tang name) as 'Choshukyu' in the analogy form of Gokanjyo (The History of the Later Han Dynasty) or 'Shobo' or 'Shotei' as an example of the Han dynasty age. In the Japanese name, they were called 'Murasaki no kumo' (meaning 'purple colored cloud') as seen in Yakumo misho (a book on tanka poetics written in Kamakura era) and Goshui wakashu (Later gleanings of Japanese poems).
It was also read 'Ougo.'

Under the Imperial House Act, the honorific title is 'Heika (his majesty)' but it was 'Denka' under the Taiho Code. Also, 'Taikotaigogu' and 'Kotaigogu' were both officially called 'Kisainomiya' and they are called 'Sangu' in general terms. This is the origin of 'Jugo' (honorary rank next to the three Empresses: Great Empress Dowager, Empress Dowager, and Empress) meaning treatment and title.

The title 'Kogo' was stipulated in writing after the Taiho Code was put in place, so strictly speaking, Japan's first empress was Empress Komyo, who became the empress of Emperor Shomu in 729. However, since the Kanji '皇后' (empress) is assigned for all 'Okisaki' of emperors since Emperor Jinmu in 'Nihon Shoki,' it is common practice to call wives of the emperor before her as 'Kogo' (empress).

There are no clauses that state qualifications to become the empress in the Taiho Code but since it states that 'Kisaki,' who was one rank below the empress, needed to be 'a princess with a rank above 'Shihon,' (the fourth rank of Imperial Prince's rank) by definition, people were resigned to think that the empress had to be a princess. In 'Nihon Shoki,' with the only exception of Iwanohimenomikoto, Emperor Jintoku's 'Kogo,' all fathers of 'Kogo' were either God or the Emperor/a member of the Imperial Family (But it is thought in 'Nihon Shoki' that the title 'Kogo' was presented as an honary award to the emperors' real mothers in later years). However, since Empress Komyo became empress by imperial investiture, following Iwanohimenomikoto as a precedented example, these became unrestricted and rather, the Fujiwara clan became more respected than the Imperial Family as the origin of the empress' clan.

Normally, only one person could be the empress, however, when FUJIWARA no Sadako became empress of Emperor Ichijyo in 990, despite FUJIWARA no Junshu's reign as the empress of Emperor Enyu, he allowed and enforced two empresses to co-exist, the one that was in reign and the new one. Since then, up to two people could ascend to the throne as empress simultaneously.
In order to differentiate the two, Junshu was given the Kogogushoku (officer for serving the empress in household ministry) and was called 'Kisaui no miya.' Sadako was given the Chugushiki (Office of the Consort's Household) and called 'Chugu.'
Moreover, as FUJIWARA no Shoshi was to become the empress in 1000, it became an example of one emperor having two empresses.
In this case, Sadako was re-titled 'Kisainomiya' and Shoshi became 'Chugu.'
'Kisai no miya' and 'Chugu' were both empresses and one was not superior to the other but in most cases, 'Chugu" was substantially in the position of the emperor's legal wife.

Afterward, the role of empress became diversified. In case either the mother of the emperor was already dead or the rank of the real mother was too low, 'Junbo' (a woman who was given the status equivalent to the emperor's birth mother) was assigned to be the mother. The first example of such is Imperial Princess Teishi who became 'Junbo' for Emperor Horikawa in 1091 but since she became the empress at the same time, women who were not wives of the Emperor started to be represented as empress. Such empresses are scholarly called 'Hisaigou no Kogo' (an empress who is not wife of an emperor) and there are eleven of these cases in total. Administrative terms set by the Imperial Household Agency refer to them as 'Sonsho Empress' (Honorific empress who is not a wife of the Emperor).
Teishi was a 'Chugu' but all empresses who were 'Hi saigou' were 'Kisainomiya.'
In later years, there were cases when the title 'Kisai go' was given even if she did not have experience as 'Junbo,' for the purpose of favorably treating unmarried princesses. In addition, in 1134, FUJIWARA no Taishi, who entered into court (Imperial Consort) as the wife of Emperor Toba after he abdicated and retired, became empress ('Kisainomiya') in order to clarify that she is the legally wedded wife of Chiten (emperors or retired emperors). Moreover, Toba made FUJIWARA no Tokuko, who was the real mother of his last son, Emperor Konoe, an empress, based on the fact that she was his real mother. Others include three women who were conferred the court rank 'empress' posthumously.

The period of the Northern and Southern Courts (in Japan) onward, Imperial Princess Junshi, the wife of Emperor Godaigo was the last to become empress (Chugu) in 1333 and the empress by Imperial Investiture ended. It was revived, for the empress of Emperor Gomizunoo (Chugu), Masako TOKUGAWA, when she became the empress in 1624.
Afterward, two empresses were no longer in place and all empresses became 'Chugu.'

In 1868 (the start of the Meiji era), the title 'Chugu' ended since Shoken Taigo, who was Emperor Meiji's wife, became 'Kisainomiya' the following year.
When the former Imperial House Law was issued, the capacity for the empress became one, the title 'Chugu' was officially abolished to be unified as 'Kogo.'
The 'Junbo' system was also abolished. It was since this time when empresses whose fathers were not of the Imperial Family were admitted as a member of the Imperial Family.

Ranks of empress in China

In Chinese past dynasty, there were empresses who were the wives of the emperor. In "Onmyo-gogyo-setsu" (The Theory of Five Elements), men were classified as 'Yin' and women as 'Yang'; the culmination of each was the Emperor and Empress respectively. For this reason, similar to the emperor holding bureaucracy of those below Sankokyukei (three ministers and nine councilors), the Kokyuseido (an institution where an emperor has multiple wives in order to maintain the imperial line) also had a hierarchy where the number of empresses tripled; San (three) fujin, Kyu (nine) no hin, Nijyunana (twenty-seven) no seifu, and Hachijyuichi (eighty-one) no gyosai.

There is no family name for the Japanese Imperial Family but the Chinese past monarchs had a family name and in principle, women with a different family name became the empress. Therefore, Chinese empresses were called by their original family name and empress of the Koso, the Third Emperor of the Tang Dynasty, originated from a family with 'Bu' (武) so her official name was 'Empress Mu'(武皇后). However, she usurped the title and called herself empress, at the same time, she started a new dynasty and named it Shu (called Bushu). As the empress, Busho is called Busokuten. She is the only empress in the past Chinese dynasty.

Ranks of empress in countries other than Japan and China

Initially, the title 'empress' was addressed to the legally wedded wives of the emperor under the political view of the world set up by the past Chinese dynasties. Therefore, in nations that use Chinese characters, if the title for the highest ranking monarch's is emperor or something of equivalence, empress was present. Kings' (and Guno, a second highest rank of the court rank in China) existed as monarchs in reign of one region/one race under the emperor.

Even in nations that do not use Chinese characters, there are cases where a monarch who reigns over several regions or nations is superior to a king who reigns over only one region or one nation. Such a monarch is customarily translated as 'Kotei' (皇帝) in Japanese.
To this end, title for the wife of the monarch with the title that is translated as 'Kotei' is also translated as 'Kogo.'

Translations for emperor

Imperator, one of the titles for the monarch in the Roman Empire, is usually translated as 'Kotei' and the family name Caesar became a title for the monarch, which was used as a title for the ruler and monarch in societies that inherit the history of East Western Roman Empire, and it also translated as 'Kotei.'
The Persian Empire of the Sassanid Dynasty, the 'King of King (Shahanshah)' of Iran's Pahlavi Dynasty, 'Sultan' or 'Padishah' of Ottoman Empire, the Ethiopian 'King of King (Negusa nagast)' in North Africa, 'Padishah' of the Mughal Empire in India, 'Sapa Inca' of the Inca Empire in South America are translated as 'Kotei.'
If these monarchs adopted the monogamous system, the title for the wife would have been 'empress' but in fact, alias that are normally used by researchers and custom take precedence so it is not uniform.

In societies with the monogamous system, such as the West European Christian societies, there is only one official wife of the emperor and it is common to be translated as 'Kogo' or 'Kohi,'
An example is Theodora, who was the wife of Emperor Justinian I., the Eastern Roman Emperor. Her position is translated 'Kogo' or 'Kohi' (both meaning empress).

Kogo and Jyotei (empresses)
In European languages, generally, the title that means 'Kogo' in Japanese is translated as 'Kotei' in the feminine form (in fact, most titles for the ruler and peerage follow suit). In this case, it cannot be distinguished from the title whether she is the wife of the emperor or the empress who attained the crown.
When translating in Japanese, the former needs to be translated as "Kogo" and the latter, 'Jyotei.'
The aforementioned Theodora is after all, 'Kogo.'

Catherine II of Russia was initially the wife of Peter III who reigned as empress herself due to a coup so she is the same person. However, title in Russian is the same word but distinguishes it with 'Kogo' and 'Jyotei,' before and after her enthronement.
Maria Theresa, the wife of Francis I, Holy Roman Emperor (the Holy Roman Emperor) would be 'Kogo' but as she was practically the ruler, serving also as the Queen of Bohemia, she is often translated as 'Jyotei.'