effort: often suggests a single action or attempt OR persistent activity and implies the calling up or directing of energy by the conscious will: made the supreme ~ and crossed the finish line first.    （direct这里表示用于或对准to use for or aim at ，如we need to direct our attention to this problem我们需要注意这个问题，即把注意力对准或用于，如most of his anger was directed against himself他主要是生自己的气，即把愤怒对准或用到，was that remark directed at me那话是针对我吗）    energy和power都表示力没有本质区别，power泛指，energy特使"被储存"的力，称为能量，见20190618 力量power-might      


exertion: may describe the bringing into effect of any power of mind or body or it may suggest laborious and exhausting effort: a job not requiring much physical ~.     labor费力劳动implies great and often strenuous, onerous and fatiguing exertion巨大艰苦沉重劳累地劳动，特别是体力劳动，如believes the farmers are poorly paid for their labor认为农民的费力劳动没有得到合理报酬      exhaust表示用尽to use up，如力量资源耐心


pains: implies toilsome or solicitous effort by a conscientious agent: took ~ to do the job well.    （toil指长期巨大努力prolonged labor, 如his lot would be years of back-breaking toil他的命运将是多年的辛劳，如Churchill丘吉尔的《Blood, Toil, Tears, and Sweat鲜血辛劳泪水汗水》)     solicitous操心的   谚语no pains no gains不劳无获中，pains即指长期巨大操劳努力，又如本例    （conscientious勤勉认真的taking care to do things carefully and correctly，如a conscientious student/teacher/worker勤勉认真的学生/一丝不苟的老师/认真负责的工人，注意conscientious有两个i，发音和拼写时不要漏了）


trouble: implies effort that inconveniences or wastes time and patience: went to a lot of ~ to get the right equipment.    （convenience方便便利，是指既有用又容易用both useful and easy to use，如we have provided seats for the convenience of our customers为方便顾客我们备有座位，如he was happy to make a detour for her convenience为了她方便他乐意绕道，如for (the sake of) convenience , the two groups have been treated as one in this report为方便起见，这两个组在本报告中被视为一组，如convenience store便利店(一般24小时营业)，public/modern convenience公共厕所/现代便利设施）   又如谚语never trouble troubles till trouble troubles you不要自找麻烦，除表示麻烦找麻烦，trouble还表示困难疾病故障动乱等，十分常用


effort努力: 指有意识地唤起和使用能量，持续性或结束性，exertion努力: 指费劲竭力的努力，pains努力: 指长期操劳的努力，trouble麻烦: 指不方便，浪费时间和耐心的努力


记忆方法: 1）首字母EEPT是竞争comPETE的后四个字母<==努力       "努"意思很简单: "尽量使出力气"，如汉乐府的少壮不努力老大徒伤悲，如陶渊明的及时当努力岁月不待人；另外努还表示"突出"，如努嘴

         2）努力的意思是积极用力mean the active use of energy in producing a result.