by the way

[by the way] also [by the bye] {adv. phr.} Just as some added factor news; as something else that I think of. - Used to introduce something related to the general subject, or brought to mind by it.

We shall expect you; by the way, dinner will be at eight.

I was reading when the earthquake occurred, and, by the way, it was The Last Days of Pompeii that I was reading.