counter for generations
Used with numbers to count generations, reigns, or dynasties. Often seen in historical or family contexts.
Louis XIV was a king of France.
Geological suffix for naming epochs, such as 更新世 (Pleistocene). Not used as a standalone word for 'epoch'.
The 15th Tokugawa shogun was Yoshinobu.
The Pleistocene is also called the Ice Age.
世 counts successive holders of a hereditary title such as a shogun or pope, while 代目 is the everyday counter used for things like company presidents, sumo wrestlers, or kabuki actors.
From Middle Chinese 世 (sjèjH, 'generation, epoch'). Used in Japanese as a counter and suffix with the on'yomi reading せい.