faithful: implies unswerving adherence to a person or thing or to the oath or promise by which a tie was contracted: ~ to her marriage vows.    a tie was contracted形成关系，contract合同、签合同      （promise，oath和vow都是承诺，表示答应要做某事或不做某事，promise泛指承诺、不正式，如I promise to help you with your homework tomorrow我答应帮你写作业；oath是正式承诺，常在正式场合，如保证说真话或坚守某种价值，常有法律或宗教意义，如I took an oath to tell the truth in court我在法庭承诺讲真话；vow是庄严的承诺，常和个人相关，如结婚、宗教效忠，通常有强烈的感情色彩，如they exchanged vows to love and support each other for life during their wedding ceremony婚礼上他们承诺永远互爱互助）


loyal: implies firm resistance to any temptation to desert or betray: the army remained ~ to the czar.    desert抛弃


constant: stresses continuing firmness of emotional attachment without necessarily implying strict obedience to promises or vows: ~ lovers.


staunch: suggests fortitude and resolution in adherence and imperviousness to influences that would weaken it: a ~ defender of free speech.    fortitude坚忍坚韧: 坚强地忍受艰苦和困难firm in enduring physical or mental hardships and suffering          fortitude and resolution的首字母FR联想法国人，有韧性有决心


steadfast: implies a steady and unwavering course in love, allegiance, or conviction: ~ in their support of democratic principles.   steady稳定，表示不间断不震动    waver特指做出决定后又犹豫动摇


resolute: emphasizes firm determination to adhere to a course or purpose: ~ in his determination to see justice done.     staunch和resolute都表示坚定的决心，程度最强，steadfast则强调不动摇

faithful忠诚：泛指对人或事或承诺的坚持(unswerving adherence)，loyal忠诚：表示能抵抗抛弃背叛等诱惑，constant忠诚：强调持久忠诚，无论是否严格，staunch忠实：强调坚韧不动摇的决心，steadfast忠实：对感情誓言信念等的坚定不移，resolute坚决：强调坚定的决心做某事

记忆方法： 1）首字母FLCSSR排列成LF龙凤和SSRC时时如此<==优秀的人时时忠实         "忠"，从心中声，本义为"尽心竭力、竭诚"。中和心合用表示"心意集中，心无旁骛"，也就是竭诚、尽心竭力。如忠诚忠信忠厚忠实效忠忠于人民/婚姻/誓言/家庭，古代特指对君主尽心竭力，即忠君

           2）忠实的意思是坚定效忠mean firm in adherence to whatever one owes allegiance.