1.
alternate attendance, sankin-kōtai
A system during the Edo period (1603–1868) that required feudal lords (daimyō) to alternate their residence between their home domains and Edo (present-day Tokyo). This compelled lords to spend roughly every other year in Edo, keeping their families there as de facto hostages, which served to maintain the shogunate's control.
The feudal lords traveled back and forth between Edo and their domains under the alternate attendance system.
Etymology
Formalized by the third Tokugawa shogun, Iemitsu, in 1635. The system required 大名 to maintain residences in both their home 藩 and in 江戸, and to travel between them on a fixed schedule. The enormous expense of maintaining two households and funding the elaborate processions (大名行列) depleted the lords' wealth, making it difficult for them to fund military challenges to the shogunate. The system also contributed to the development of roads and post towns across Japan.