Kotaigo (Empress Dowager) (皇太后)
Kotaigo, or empress dowager (pronounced "huang tai hou" in Chinese), is a title held by the widow of a deceased emperor or a term used to refer to such a person. It is also abbreviated as Taigo. It is one of the Sangu (three empresses) together with the Empress and Grand Dowager Empress. In addition, it was also referred to as In meaning the retired emperor (or cloistered retired emperor) or, collectively with dominant nobilities and temples and shrines, as Ingu (imperial lady) or Ingu oshinke (a general term for imperial families and nobles who gathered strength by approaching the Emperor's power).
At present, the Imperial House Act determines that the title of honor for it is 'her Majesty' but, in old days, it was honorably referred to by adding a letter 'Miya (imperial princess, etc)' as in Kotaigo-Miya.
It was read as 'Okisai-no-miya.'
In China, from the periods of Qin and Han to the period of Qing, the real mother of the Emperor in reign and the former Empress were respectfully referred to as 'Empress Dowager.'
In Japan, even though in the Nara and Heian periods, there were cases where an honorary title of Kotaigo or Kotaifujin (title for previous retired emperors' wife) were dedicated only because the person was the real mother of the Emperor of the time, there is no such example since the early stage of Edo period and it has become a practice that the lawful wife of the former Emperor is named the Taigo.
In addition, Omiya gosho refers to the residence of the Empress Dowager and the section which takes care of the Empress Dowager is referred to as kotaigo gushiki (Imperial Household Agency employee assigned to the household of Empress Dowager).
Usually, Kotaigo is not used as a posthumous title for a person who was an empress but, by way of exception, it is used for Empress Dowager Eisho who was the Empress of Emperor Komei and Empress Dowager Shoken who was the Empress of Emperor Meiji.
Title of 'Queen Dowager'
Refer to enQueen Dowager
For an O (king), there applies a word 'Otaigo (in English, Queen Dowager)' but from an old custom of protocol to refer to all heads of the state as Emperors, this word has not ripened as a Japanese and Kotaigo is applied. Representative example of use is Elizabeth Bowes-Lyon, the mother of Elizabeth II, the queen of England.