形容詞 confidential:

1. entrusted with private information and the confidence of another
2. (of information) given in confidence or in secret
   同義詞：secret
3. denoting confidence or intimacy
4. the level of official classification for documents next above restricted and below secret; available only to persons authorized to see documents so classified

1. A doctor who gives away confidential information about patients is not behaving professionally.
   醫(yī)生把病人的私人資料透露出來是違反職業(yè)道德的。
2. Don't repeat what I said (to anyone) it's confidential.
   別把我的話告訴別人--這是秘密。
3. I must stress that what I say is confidential.
   我要強調我說的話是保密的。
4. He has been on confidential missions to Berlin.
   他前往柏林執(zhí)行秘密任務。
5. Don't be too confidential with strangers.
   不要過份相信陌生人。
6. He told me the confidential information.
   他向我透露了這個秘密的信息。

con.fi.den.tial

adj.Abbr. conf.（形容詞）縮寫 conf.
Done or communicated in confidence; secret.
秘密的：秘密地進行或交流的；秘密的
Entrusted with the confidence of another:
可信任的：對另一個人寄以信任的：
例句：
a confidential secretary.
機要秘書

Denoting confidence or intimacy:
親密的：表示信任或親密的：
例句：
a confidential tone of voice.See Synonyms at familiar
親密的聲調參見 familiar

Containing secret information, the unauthorized disclosure of which poses a threat to national security.
機密的：包含機密信息的，未經授權泄露可能會危及到國家的安全的

【引伸】
con.fiden.tial.ity
con.fiden.tially
adv.（副詞）