循环的英文：
circle
loop
circulate

参考例句：

The seasons rotate.
四季循环。

loop initialization
循环初置(初始状态的),循环初始化

The backwater recirculates
回水是反复循环。

The refrigerant in a household refrigerator also undergoes a cyclic process
家用冰箱的致冷剂，也经历循环过程。

Exercise helps the blood and other body fluids to circulate.
锻炼帮助血液和其它体液循环。

The last figure of the decimal 0.63 repeats.
小数0.63的末位数是循环的。

Although oxygen does not participate directly in the citric acid cycle, the cycle operates only when O2 is present.
尽管氧气没有直接参与三羧酸循环，循环却只有在氧气存在时才能进行，

This material is recyclable and will not pollute the environment.
这种材料是可循环利用的，因而不会污染环境。

Oxaloacetate is formed in the last step of the citric acid cycle by the NAD+-dependent oxidation of L-malate.
草酰乙酸在三羧酸循环的最后一步通过NAD+-依赖的L-苹果酸的氧化来合成。

"Wet beriberi is more acute, with edema from cardiac failure and poor circulation."
湿性脚气病病情较急，会有心力衰竭、循环不良及主要由此造成的水肿。

circle是什么意思：
n. 圆，环；周期；循环；圈子
v. 盘旋；环行

circle of longitude
经度圈;经度圈;黄经圈;黄纬圈

circle of declinatio
赤纬度盘;赤纬圈;时圈

This is a chord of a circle.
这是个圆的弦。

loop是什么意思：
n. 环，圈；回路；弯曲部分；翻筋斗
v. 打环；以环连结；（使）翻筋斗

The airman looped the loop eight times.
那位飞行员作了八次翻筋斗的飞行表演。

The plane looped the loop three times.
飞机连翻了三个跟头。

Loop the tree with a rope = loop a rope around the tree
将绳子卷绕于树

circulate是什么意思：
n. 循环，环行；传播，流传；流通；在人群中周旋；发行，销售

Have you been circulated with details of the conference?
你收到会议详情的通知了吗？

circulate counterfeit coins
使伪造的钱币流通

This magazine has a large circulation.
这本杂志发行量很大。