Rangaku (Kyūjitai: 蘭學/Shinjitai: 蘭学, literally "Dutch Learning", and by extension "Western Learning") is a body of knowledge developed by Japan through its contacts with the Dutch enclave of Dejima, which allowed Japan to keep abreast of Western technology and medicine in the period when the country was closed to foreigners, 1641–1853, because of the Tokugawa shogunate's policy of national isolation (sakoku).