在常用词bicycle中有个表示数目的前缀bi-，它源自拉丁语 bis，愿意为twice。bi-最早出现在从法语或拉丁语引进的外来语中，是个只与拉丁词根结合的原生词缀。16世纪以后，bi-成为英语中的派生词缀，能与名词、形容词及副词相缀合，构成新词（其中包括生物学与化学的术语），表示two，double, having two, in two ways等含义。bi-在个别单词中读[bi](如bigamy)， 一般读[bai]。bin-是bi-的异体，只出现在以元音字母开头的词根中。

先介绍几个以bi-(bin-）开头的原生派生词。

bicycle [ bi- = two 二； cycle = wheel 轮 =>“a vehicle with two wheels有两个轮子的交通用具”→]n . two-wheeled vehicle driven by pedals 脚踏车 / I go to school by bicycle.我骑自行车上学。

bicyclist n. 骑自行车的人

bicameral [ bi- =two 二 ; camer = chamber 室;-al a . = of …的=>“of two chambers 两室的”→]a. having two legislative chambers 两个议院的，两院制的 / The United States Congress is bicameral.美国国会是两院制的。

biennial [ bi- = two 二; enni = year 年；-al a . = of ...的=>“of two years 两年的” →]a. lasting two years; once every two years 持续两年的；两年一度的 / He has finished his biennial postgraduate course. 他已修完了两年的研究生课程。

bigamy [ bi- = two 二; gam = marriage 婚姻；-y n . = the state of …的状态=> “the state of keeping two marriages at the same time同时维持两个婚姻关系的状态”→]n. the practice of having two wives or two husbands at the same time 重婚 / Bigamy is unlawful in most countries.在多数国家里，重婚是非法的。

bigamist n. 犯重婚罪的人 

bigamous n. 重婚的，犯重婚罪的