(1) ①often意为“常常，时常”，表示“不同场合下的经常”，强调经常发生的次数。通常置于主要动词前，或be动词后，在有助动词时，置于助动词后。
- They often go to the countryside to give performances.
他们常去农村演出。 - I have often thought of making researches as Darwin did.
我常常想要像达尔文那样做研究。 - How often do the buses run?
公交车多长时间一趟？
②often有时放在句末，特别强调时放在句首。
- I don't get to London very often .
我不常去伦敦。 - Often I did not see Papa until the evening.
我常常直到晚上才见到爸爸。
③有时often可作为表语。
- We see him when he comes to town, but that isn't very often .
他来城里时我们能见到他，但并不经常。
(2) frequently意味着同一场合下动作频繁地(可能略有间隔)多次重复，强调频度，常用于书面语。
- “Of” is probably the most frequently used of all the English prepositions.
“of”可能是所有英语介词中用得最频繁的一个词。 - Yesterday I frequently made mistakes in my lecture.
昨天我在讲课中屡屡出错。
