tannin
noun [ C or U ] uk/ˈtæn.ɪn/ us/ˈtæn.ɪn/ (also tannic acid, uk/ˌtæn.ɪkˈæs.ɪd/ us)
丹宁（酸），鞣酸
(one of) a group of chemicals that are found in plant cells, especially in leaves, bark (= a tree's outer covering), and fruit that is not yet ready to eat