[qí shí]
actually; in fact; as a matter of fact; really; in reality; in truth
In fact that was not the case.
其实不然。
He is in reality penniless.
其实他身无分文。
He appears to be strong and healthy, but, as a matter of fact, he suffers from a very weak heart.
他看上去强健,其实他的心脏很衰弱。