merry: suggests cheerful, joyous, uninhibited enjoyment of frolic or festivity: a ~ group of holiday revelers.    merry程度很强，除了merry Christmas，和the more the merrier（人越多越好，如有人问我可以带朋友来么，可以这么回答）以外，常暗含贬义        revel的名词1个l或2个l都正确      frolic嬉戏;嬉闹  


blithe: suggests carefree, innocent, or even heedless gaiety: arrived home late in her usual ~ way.   gay做形容词时强调完全没有忧虑，精神焕发洋溢，由形容词变名词时，变y为i加ety   解释blithe的4个词都表示无忧无虑、不考虑


jocund: stresses gladness marked by liveliness, elation and exhilaration of spirits: good news had left him in a ~ mode.    解释jocund的4个词都有字母L


jovial: suggests the stimulation of conviviality and good fellowship or the capacity for these: grew inceasingly ~ with every drink.      convivial表示人或环境欢乐友好轻松cheerful, friendly, and relaxed，如a convivial evening/atmosphere/company欢乐的夜晚/轻松友好的气氛/快乐开朗的伙伴


jolly: suggests high spirits expressed in laughing, bantering, and jesting and a determination to keep one's companions easy and laughing: our ~ host enlivened the party.

merry欢乐快活: 表示尽情玩乐，blithe欢快: 强调无忧无虑，jocund欢快: 常形容欢快开朗的心情或性格，jovial愉快友好: 表示愉快而友好，jolly欢快: 常表示欢笑逗趣 的快乐景象(如解释中的lauth,banter,jest开怀大笑打趣玩笑)

记忆方法: 1） 首字母MBJJJ中的BM想成不忙，JJJ中的J想成Joy快乐，3J表示非常快乐<==欢乐    "乐"本意表示一种弦乐器，繁体是"樂"，引申为愉悦。欢则表示"高兴"。
         
         2）欢乐的意思是高兴轻松mean showing high spirits or lightheartedness.