～というのは事実だ

About

The ～というのは事実じじつだ pattern is used to indicate that the preceding phrase is a "fact" or "the truth". It makes use of ～という, which refers to the previous noun/phrase, 事実じじつ "reality", and the auxiliary verb だ. ～というのは事実じじつだ is often translated as "It is a fact that..." or "The truth is...".

E.g. あの人ひとが事故じこを起おこしたというのは、事実じじつだ。 "It's a fact that that person caused the accident."

It's also quite common to omit という altogether. This is more common in spoken Japanese, and places slightly less emphasis on the information preceding のは.

E.g. あの日ひが非常ひじょうに暑あつかったのは事実じじつだ。 "It is a fact that that day was very hot."

It's also possible to set up an "It is a fact that X, but..." style statement, by following 事実じじつだ with any "but" variation (e.g. が, けど, etc).

E.g. 納豆なっとうが体からだにいいというのは事実じじつだが、私わたしは食たべれない。 "It's a fact that natto is good for your body, but I can't eat it."

Summary

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  ～というのは事実じじつだ means "It is a fact that..."

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  Omitting という to form the ～のは事実じじつだ pattern is also possible