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


loyal: implies firm resistance to any temptation to betray or desert: 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.


steadfast: implies a steady and unswerving course in love, allegiance, or conviction: ~ in their support of democratic principles.


resolute: emphasizes firm determination to adhere to a course or purpose: ~ in his determination to see justice done.

faithful泛指对关系(tie)的不变坚持，loyal强调拒绝诱惑，constant连续坚定但可能不严格信守承诺，steadfast坚持不变道路爱信义，resolute: 坚定决心于道路目标，staunch: 坚忍和决心(fortitude & resolution, 联想法国人FR)。

这几个词是强烈褒义词，但都不好记，

记忆方法： 1）首字母FLCSSR


           2）staunch和resolute都表示决心，程度最强，联想法国人(Fortitude & Resolution)有决心。


          3）忠心的意思是坚定效忠mean firm in adherence to whatever one owes allegiance.