often: tends to stress the number of times a thing occurs without regard to the interval of recurrence: they ~ come to dinner.


frequently: usually emphasizes repetition, especially at short intervals: saw her as ~ as he could.


oft: close to often in meaning, is used chiefly in compound adjectives: an ~-told tale; or occasionally in formal discourse: a man ~ seen but seldom understood.   如an oft-repeated story经常说的故事    （discourse 1、论文、演讲a long and serious treatment or discussion of a subject in speech or writing，如a discourse on issues of gender and sexuality关于性别和性行为的论文，如he was hoping for some lively political discourse at the meeting他希望在会上听到些生动的政治演讲   2、语言学中的语篇、话语the use of language in speech and writing in order to produce meaning; language that is studied，如spoken/written discourse口头/书面语篇，如discourse analysis语篇分析）


oftentimes: may be preferred for intonational reasons or as a more florid word: a demeanor ~ vague and distracted.  如oftentimes, he is the only one in the aerobics class经常地，他是唯一去上有氧健身课的人     intonation语调，指声音的升降the rise and fall of the voice in speaking   florid语言华丽的，注重修辞的using unusual words or complicated rhetorical constructions  


often经常: 强调次数多，无论间隔长短，frequently频繁: 也强调次数多，且间隔短，oft经常: 同often，用于复合形容词和正式文体，oftentimes经常: 同often，用于调整语调或词藻

记忆方法: 1）首字母OFOO中O出现3次<==经常

         2）经常的意思是短时间内反复发生mean again and again in more or less close succession.    again and again反复一再再三