知 is a fundamental character: 知道 (zhīdào, to know), 知识 (zhīshi, knowledge), 通知 (tōngzhī, to notify), 知名 (zhīmíng, well-known), 未知 (wèizhī, unknown).
culture
The Confucian saying 知之为知之，不知为不知 (zhī zhī wéi zhī zhī, bù zhī wéi bù zhī) — 'To know what you know and know what you don't know, that is true knowledge.'
