Thursday，2025.10.16
New words：
vain [veɪn] adj.徒劳的；枉然的；无结果的；自负的
in vain [veɪn] 徒劳;白费力气；无用的;无意义的;无价值的
“vain” 的核心词根是拉丁语 “vanus”（意为 “空的、虚无的；徒劳的”）
Sample Sentences：
We made a vain attempt. / We attempted in vain.
I knocked loudly in the vain hope that someone might answer.
She closed her eyes tightly in a vain attempt to hold back the tears.