apropos
adverb, preposition formal uk/ˌæp.rəˈpəʊ/ us/ˌæp.rəˈpoʊ/
说到…；关于…；就…而言
used to introduce something that is related to or connected with something that has just been said
apropos of I had an email from Sally yesterday - apropos of which, did you send her that article? 我昨天收到萨莉的一封邮件——对了，你把那篇文章寄给她了吗？
Apropos what you said yesterday, I think you made the right decision. 至于你昨天说的话，我觉得你作的决定是对的。
apropos
adjective [ after verb ] formal uk/ˌæp.rəˈpəʊ/ us/ˌæp.rəˈpoʊ/
适时的；恰当的
suitable in a particular situation or at a particular time
apropos to clothes that are apropos to the occasion 适合那个场合穿的衣服