by the way

by the way

Incidentally; on a side note. An interjection meant to casually introduce or emphasize additional information in the conversation. By the way, I remembered where I left my keys, in case you were wondering. Beckett was an amazing playwright. There's a lecture on his work tomorrow, by the way.
See also: by, way
Farlex Dictionary of Idioms.

by the way

 and by the by 
1. a phrase indicating that the speaker is adding information. (By the by is not as frequent.) Tom: Is this one any good? Clerk: This is the largest and, by the way, the most expensive one we have in stock. Bill: I'm a realtor. Is your house for sale? Alice: My house is not for sale, and, by the way, I too am a realtor.
2. a phrase indicating that the speaker is casually opening a new subject. Bill: Oh, by the way, Fred, do you still have that hammer you borrowed from me? Fred: I'll check. I thought I gave it back. Jane: By the by, don't you owe me some money? Sue: Who, me?
See also: by, way
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs.

by the way

1. In passing, incidentally, as in She's my wife's cousin, and by the way, a good friend. [Mid-1500s]
2. Parenthetically, in addition, as in We saw Mary last week, and by the way, did Tom call you? [Early 1600s]
See also: by, way
The American Heritage® Dictionary of Idioms by Christine Ammer.

by the ˈway

(also by the ˈby/ˈbye less frequent) (spoken)
1 used for introducing something you have just thought of, which may or may not be connected to what has just been said: I had a meeting with Graham at work today... by the way, I’ve invited him and his wife to lunch on Sunday.
2 used for saying that something is not important in the present situation or discussion: Her academic qualifications are by the by. What we need is someone dynamic and creative.
See also: by, way
Farlex Partner Idioms Dictionary

by the way

Incidentally: By the way, you forgot to cash that check.
See also: by, way
American Heritage® Dictionary of the English Language, Fifth Edition.
See also:
  • by the by
  • by the bye
  • dynamite
  • boom goes the dynamite
  • amirite
  • oh really
  • cool
  • hear, hear
  • hear, hear!
  • bonus