apropos

/ˌæp.ɹəˈpəʊ/

adjective

Meaning

Of an appropriate or pertinent nature.
By the way, incidental

Synonyms

by the way,

incidental,

incidentally

adverb

Meaning

By the way.
Timely; at a good time.
To the purpose; appropriately.

preposition

Meaning

Regarding or concerning.

Synonyms

about,

as for