efore与by before 指“在……之前” : Please come before ten o'clock.请10点以前来. by 指“在……前(时间);截至(到)……”: How many English books had you read by the end of last year?到去年年底以前你看过多少本英文书? 表示“在……以前”时,before 与 by 基本可通用.但 by 还有“截至……为止”之意: How many models have you made by the end of last month?截至上月底你做了多少个模型?