extra

…a specially issued publication by a newspaper company to inform readers of a major, unexpected event. Because breaking news is important, extras were also issued in other countries when a major event occurred, such as a war or an assassination. However, in Japan, this is especially common because multiple newspapers in the same city (Tokyo, Osaka) competed to provide breaking news.

*Some terminology explanations that mention "extra" are listed below.

Source | Heibonsha World Encyclopedia 2nd Edition | Information

…新聞社が重大な突発事件を読者に速報するために臨時に発行する印刷物。速報に意義があるため，外国でも戦争や暗殺など大事件では号外extraが発行された。しかし日本では，同一の都市(東京，大阪)で複数の新聞が速報を競ったため，ことに多い。…

※「extra」について言及している用語解説の一部を掲載しています。

出典｜株式会社平凡社世界大百科事典 第２版について | 情報