root word：circum (around) come from circle.
circumnavigate vt.环航 circum + navigate
circumstance n. 形式，情况 circum + stance
circumcision n. 包皮环切， 割礼 circum + cis(scissor,切)+ ion
circumference n.园周，周围 circum + ference(fence)
circumlocution n.迂回说话，托词 circum + loccution(location)
circumvent vt. 克服，回避，绕过 circum + vent (went)
circumscribe vt.划范围， 限制 circum + scrible
circulation n.流通，循环
circulatory abj.(血液)流通的，循环的
circulator n.传播者， 循环电路