often vs frequently

often and frequently both are adverbs.

Word	Noun	Adjective	Verb	Adverb
often	No	No	No	Yes
frequently	No	No	No	Yes

As adverbs, often and frequently are synonyms defined as:

Other synonyms of often include oft, oftentimes, ofttimes.

often (adverb)	frequently (adverb)
many times at short intervals	many times at short intervals
frequently or in great quantities
in many cases or instances