This is the 12210th most frequent Korean word.
다는
"다는" is a particle used to quote or express what someone says, thinks, or asserts in Korean.
'다는' is used here to connect a reported clause to a main clause, indicating that the content of the reported clause ('그가 공부를 열심히 한다') is being stated or described.
그가 공부를 열심히 한다는 말은 사실입니다.
The statement that he studies hard is true.
'다는' serves here to transform the embedded clause ('그녀가 유명하다') into a noun phrase ('그녀가 유명하다는 것'), which acts as the object of the verb '알게 되다'.
나는 그녀가 유명하다는 것을 알게 되었어요.
I came to know that she is famous.
'다는' is used to turn the descriptive clause ('한국 음식이 맛있다') into a concept ('한국 음식이 맛있다는 점') that partakes in further discussion or agreement.