This word’s versatility makes it quite useful.

apropos (ap·ro·pos): / ap ruh POH /
adverb

(1) at the right or opportune time; seasonably; fitting; to the purpose
(2) by the way; incidentally (formal)

adjective

(1) pertinent; opportune and relevant; just right

apropos of
preposition (idiom)

(1) with regard or respect to; on the subject of; with reference to; concerning (formal)

[From French à propos meaning “to (the) purpose,” a translation of Latin ad propositum.]

Usage: Your apropos remarks communicated precisely what the audience needed to hear.