matter of fact
matter of fact  {n. phr.}
Something that is really true; something that can be proved. 
The town records showed that it was a matter of fact that the two boys were brothers.
It is a matter of fact that the American war against England was successful.
- Often used for emphasis in the phrase "as a matter of fact". 
I didn't go yesterday, and as a matter of fact, I didn't go all week.
Mary wasn't wearing a blue dress. As a matter of fact, she hasn't got a blue dress.
Contrast: MATTER OF OPINION.
Categories: 
 
Source: A Dictionary of American Idioms
