by-是本族语的前缀，它的前身是古英语的bi-，其意思相当于secondary或near by。作为形容词性的派生前缀，它主要加缀在名词之前，构成新的名词。by-是个活性词缀，在含有by-的派生词中，词汇历史较短的，往往还带着连字符（-)。下面介绍几个含有by-的派生词。

bypass [ by- = secondary 次要的；pass n. 道路=>“a secondary pass 次要的道路” →]n. passage or road to one side of the main passage 旁道，旁路 / Take the bypass to avoid the traffic in the centre of town.抄旁道避开交通拥挤的市中心吧！

bystander [ by- = near by 附近;stand v. 站立；-er n. = a person…者=>“a person who stands near by 站在附近者”→ ] n. person who stands near but does not take part 旁观者 / The police asked some of the bystanders about the accident.警方向一些旁观者查问该事件。

bywork [ by- = secondary 次要的；work n. 工作=>“ secondary work 次要的工作”→] n . work done by the way, in intervals of leisure 业余工作 / He is a teacher; writing is his by work.他当教师，写作是业余工作。

by-product [ by- = secondary 次要的；product n. 产品→]n. secondary result produced in making the main product 副产品 / Kerosene is a by-product of petroleum refining.煤油是精炼石 油时的副产品。