n(1)循环(series of related events repeating in a regular order)[C]：the～of the seasons/birth and death/economic booms and slumps季节/生与死/经济繁荣与萧条的循环;the trade～贸易循环;a vicious～恶性循环;Life follows its usual～： birth，youth，old age and death.生命总是遵循由出生、青年、老年直至死亡的过程发展。

(2)周期(period of time needed for this to be completed)[C]：a 50-second～50秒的周期;a～of alternating current交流电的周期;the gasoline-engine/breeding/sunspot～汽油机/繁殖/太阳黑子的周期;

(3)系列，全集(套)(complete set or series，eg of songs or poems，that deal with a single theme or hero)[C]：a (Schubert) song～(舒伯特)组歌;the Arthurian～写亚瑟王的系列作品;the～of events leading to Hitler's downfall导致希特勒倒台的一系列事件;〖同〗series;

(4)自行车，摩托车等(bicycle，motor-cycle，etc)[C，U(by～)](infml)：a～shop/race/path自行(摩托)车商店/自行(摩托)车赛/自行(摩托)车道;My～is broken.我的自行(摩托)车坏了。go by～乘自行(摩托)车去;

→′cyclic adj 循环的，周期性的;′cyclically adv 循环(周期性)地;′cyclist n骑自行车的人;

vi骑自行(摩托)车(ride a bicycle or motor-cycle)[I，I+prep，I+adv]：go～ing骑自行(摩托)车去;～to work骑自行(摩托)车去工作;～along(a road)/into town/off home/away骑自行(摩托)车(沿路)往前走/进城/回家/离去;recommend～ing as a good form of exercise把骑自行(摩托)车推荐为一种运动的好方式;

【说明】见BICYCLE。