used to stress that something is true, especially when it's surprising
As a matter of fact, I was just about to call you.
事實上,我正要給你打電話。
used to add more information or correct something
He's not just a good player; as a matter of fact, he's the best in the league.
他不僅是個好球員;事實上,他是聯盟中最好的。