Classified
adjective
Definition
1. (adjective) Officially designated as secret and available only to authorised people — used for government documents, military intelligence, or sensitive official information.
2. (adjective) Arranged or sorted into categories or groups — used in a more general organisational sense.
3. (noun — classifieds / classified ads) Small advertisements in a newspaper or website, organised by category — jobs, property, cars, and so on.
2. (adjective) Arranged or sorted into categories or groups — used in a more general organisational sense.
3. (noun — classifieds / classified ads) Small advertisements in a newspaper or website, organised by category — jobs, property, cars, and so on.
Context Alive
You're watching a documentary about a government whistleblower who leaked thousands of files to the press. The interviewer asks what made him do it. He says he spent years working with documents marked classified that described things he believed the public had a right to know. He talks about the weight of keeping secrets that affected millions of people. The documentary ends with him living in another country, unable to come home.
Meanings
2 meanings 1 Secret — Restricted to Authorised People (Adjective) Very Common ▼
This meaning is about information, files, or material that has been officially restricted — only certain people with the right clearance are allowed to see it. Imagine a government analyst sitting in a secure room going through files stamped with a red mark — most of what they read during their working day is classified and cannot leave the building, be discussed outside, or be shared with anyone without authorisation. This is describing a formal, official status of secrecy. You might hear "that information is classified" when an official refuses to discuss something because it's sensitive, or someone could say "the documents were highly classified" about files that were restricted at the highest level of government. Or picture a journalist who receives a leaked file that was never supposed to leave a secure facility — the whole story is about how classified material ended up in the public domain. The word always implies an official decision has been made to restrict access — it's not just private, it's formally protected.
✏️ Classified exists on a scale — government documents are often ranked by sensitivity: confidential, secret, top secret. Something described simply as "classified" usually means it has some level of official restriction, while "highly classified" or "top-secret classified" signals the most sensitive level. The opposite is declassified — when previously secret documents are officially released to the public, often decades later. "That's classified" is also used humorously in everyday life when someone doesn't want to answer a question.
2 Classified Ads — Small Advertisements by Category (Noun) Common ▼
This meaning is about a specific type of advertisement — short, inexpensive notices organised into categories like jobs, housing, cars for sale, or items wanted. Imagine the back pages of a local newspaper covered in small, text-heavy boxes: someone selling a sofa, someone looking for a cleaner, a landlord advertising a flat. These are classified ads, and the section itself is called "the classifieds." This is describing a format of advertising that is simple, direct, and organised by type. You might say "I found my first flat through the classifieds" about finding accommodation through small ads in a newspaper, or someone could say "he placed a classified ad to sell the car" when describing how they listed a vehicle for sale. Or picture an online version — sites like Gumtree or Craigslist are essentially digital classifieds, where people list items by category. The word suggests a simple, practical form of advertising without the scale or cost of a full commercial.
✏️ Classified ads (or simply "the classifieds") were once the main way people found jobs, flats, and second-hand items through local newspapers. While print classifieds have largely moved online, the term is still widely used — both for the traditional newspaper version and for modern platforms like Gumtree, Craigslist, or Facebook Marketplace. You'll still hear "place a classified" or "check the classifieds" in everyday conversation.
Common Patterns
Basic Structures
classified information / documents / files → the most common combinations — officially restricted material in a government or military context
Journalists obtained a cache of classified documents that had never been meant for public release.
highly classified → restricted at the highest level — the most sensitive category of secret information
The operation was highly classified — even most of the people in the building didn't know it was happening.
classified as + noun / adjective → to be officially placed into a particular category or group
The substance was classified as dangerous and removed from sale immediately.
Common Structures
that's classified → used to refuse to give information — formally because it's secret, or humorously to avoid answering
She asked what the surprise was and he just smiled and said, "That's classified."
classified ads / the classifieds → small advertisements organised by category in a newspaper or on a website
She found her current job by browsing the classified ads in the Sunday paper.
declassify (opposite pattern) → to officially remove the secret status from a document or file — release it to the public
The files were declassified fifty years after the event and released to the national archive.
Collocations
10 collocationsclassified information
officially restricted data that only authorised people are permitted to access
classified documents
official files or papers marked as secret and restricted
classified material
any content — files, recordings, data — that has been given a secret status
highly classified
restricted at the highest level of secrecy
top-secret classified
the most sensitive category of official secret — above standard classified level
classified files
restricted records held within a government or intelligence agency
classified briefing
an official meeting where secret information is shared only with those who have clearance
classified ads / classifieds
small advertisements organised by category in a publication or website
place a classified
to submit a small advertisement to a newspaper or website
classified as
officially categorised or labelled as belonging to a particular group
Example Sentences
10 examples
1
The report was classified and could only be read by officials with the highest security clearance.
The report had been designated as secret and was restricted to officials who held the top level of security authorisation.
2
She placed a classified ad in the local paper to sell her old bicycle and had three calls by lunchtime.
She put a small advertisement in the local newspaper to sell her bike and received three enquiries before the afternoon.
3
He refused to answer the question, saying the details of the mission were still classified.
He declined to respond, explaining that the specifics of the operation remained officially restricted.
4
Thousands of classified documents were leaked to the press and published online within hours.
Thousands of secret official files were passed to journalists and appeared on the internet within a matter of hours.
5
The animal was classified as endangered after its population dropped below a critical level.
The species was officially placed in the endangered category after its numbers fell to a dangerously low point.
6
Back then, people found flatmates by posting notices in the classifieds rather than on apps.
In those days, people looked for flatmates through small advertisements in newspapers rather than using online platforms.
7
The programme was so highly classified that even senior politicians were kept in the dark about it.
The programme carried such a high level of secrecy that even senior government figures were not told it existed.
8
"I could tell you," he said with a straight face, "but then it would have to stay classified."
"I could give you that information," he said seriously, "but it would have to remain strictly between us."
9
The files were declassified in 2019 and revealed details that had been hidden for over forty years.
When the documents were officially released in 2019, they contained information that had been kept secret for more than four decades.
10
The website works like a digital version of the old classifieds — people list items for sale by category.
The platform operates in the same way as the small ads sections in old newspapers — sellers organise their listings by type of item.
Synonyms & Antonyms
6 items
Synonymsconfidential
similar in meaning but slightly softer — confidential is often used in business and personal contexts, while classified specifically implies official government or military secrecy
restricted
limited to specific people — broader than classified, which implies a formal, stamped designation of secrecy
secret
the most common everyday alternative — less formal than classified, which always implies an official decision has been made
Antonymsdeclassified
the direct opposite — previously secret material that has been officially released to the public
public
available to everyone — the opposite of being restricted to authorised individuals
disclosed
officially revealed or shared — the opposite of keeping something classified and hidden