bilateral [bi- = two 二； later = side 边;-al a. = of …的=>“of two sides 两边的” →]a. binding both sides or parties 双边的， 双方的 / The two countries signed a bilateral trade agreement. 两国签订了一项双边贸易协定。

bilateralism n. 互惠主义

binaural [ bin- ( bi-) = two 二; aur = ear 耳；-al a. = of …的 →]a. ① of or for two ears 双耳的 / The doctor wore a binaural stethoscope.医生戴着双耳听诊器。② having two speakers to give a three-dimensional auditory effect 双声道的，立体声的 / This radio set can receive binaural broadcasting.这台收音机能收听立体声广播。

binocular [ bin- (bi-) = two 二 ； ocul = eye 眼；-ar a. = of …的=>“of two eyes 两个眼睛的”→] a. for two eyes at once 双目的 / This binocular microscope is made in Germany.这台双目显微镜是德国造的。

下面介绍几个由bi-与单词结合构成的派生词。

biplane [ bi- =having two 有二个…的；plane n .飞机=> “a plane having two sets of wings 有两副机翼的飞机”→] n. an aircraft with two sets of wings, one above the other 双翼飞机 / Biplanes are rarely seen now.现在很少见到双翼飞机了。

biannual [bi-= twice 两次的；annual a. —年的→]a . twice in a year 每年两次的 / The biannual examinations are held in January and July. 一年两度的考试分别在1月与7月举行。

bisexual [ bi- = on both sides 两方面地；sexual a. 性别的=>“having both sexes 有双性的”→]a. possessing qualities of both sexes 两性的，雌雄同体的 / Bisexual animals have both male and female reproductive organs.雌雄同体的动物身上具有雌雄两套生殖器官。