名詞 classified:

1. a short ad in a newspaper or magazine (usually in small print) and appearing along with other ads of the same type
   同義詞：classified ad, classified advertisement

動詞 classify:

1. arrange or order by classes or categories
   同義詞：classify, class, sort, assort, sort out, separate
2. declare unavailable, as for security reasons
   同義詞：classify
3. assign to a class or kind
   同義詞：relegate, classify

形容詞 classified:

1. arranged into classes
2. official classification of information or documents; withheld from general circulation

1. A book containing an alphabetical or classified listing of names, addresses, and other data, such as telephone numbers, of specific persons, groups, or firms.
   通訊錄，工商行名錄，號碼簿內含按字母順序排列分類的人名、地址和其他資料的書，如特定的人、團體或公司的電話號碼
2. The books in the library are classified by/according to subject.
   圖書館的書是按照[根據]科目分類的。
3. I'm looking for the classified section. Have you seen it?
   我正在找分類廣告欄，你見到了嗎？
4. The books in the library are classified by subject.
   圖書館的書是按科目分類的。

clas.si.fied

adj.Abbr. class.（形容詞）縮寫 class.
Arranged in classes or categories.
分門別類的：劃分到階級或類別中的
Available to authorized persons only, as for reasons of national security:
機密的，保密的：只提供給獲得授權的人的，如因國家安全的原因：
例句：
a classified document.
機密文件