Explanation: Once: Wait. Waiting for the Yellow River to clear. Metaphors do not expect to achieve. Usage: Contraction type; as predicate; containing derogatory Source: Qin Hengyu "Zuo Xianggong eight": "Week of the poem reads: 'Once the river clear, life geometry?'" Examples: Really the so-called "~" it! (Tao, "the bridge")