apropos
a-pro-pos
prepositional phrase
Concerning or with reference to a particular subject.
"Apropos of nothing, he changed the subject."
adverb
Relevant or appropriate to a particular matter or situation.
"His comment was apropos the discussion."
adverb
Used to introduce a new topic or remark, meaning 'by the way'.
"Apropos, did you hear about the meeting?"
Thesaurus
Synonyms: pertinent, apt, apposite, incidentally, by the bye, by the way, well-timed, seasonably, timely
Antonyms: malapropos