Translation guide
The English word 'sleeper' has several distinct meanings. This guide covers the most common ones for learners: a person who sleeps, a train with sleeping accommodations, an unexpected success, and a spy or agent who remains inactive for a long time.
Referring to someone who is sleeping or who sleeps in a particular way (e.g., light sleeper, heavy sleeper).
A straightforward way to say 'a person who is sleeping'. Use this when you need to refer to the person as a sleeper.
隣の席の寝ている人がいびきをかいている。
The sleeper in the next seat is snoring.
Attach to adjectives to describe a type of sleeper. For example, 'light sleeper' is 眠りが浅い人 (ねむりがあさいひと) or more naturally expressed as 寝つきが悪い (ねつきがわるい) or ちょっとした物音で目が覚める (ちょっとしたものおとでめがさめる).
私は眠りが浅いので、少しの音でも目が覚める。
I'm a light sleeper, so I wake up at the slightest noise.
A train that has beds or berths for passengers to sleep in during a journey.
The standard term for a sleeper train. Note that these are now rare in Japan, but the word is understood.
寝台列車で東京から札幌まで移動した。
I traveled from Tokyo to Sapporo on a sleeper train.
Refers specifically to a sleeping car (the carriage itself).
この列車には寝台車が連結されている。
This train has a sleeper car attached.
Something that becomes very popular or successful after initially attracting little attention.
A loanword from English, commonly used in entertainment and business contexts to describe a sleeper hit.
あの映画はスリーパーヒットで、公開から数週間後に大ヒットした。
That movie was a sleeper hit; it became a blockbuster a few weeks after its release.
A more descriptive phrase meaning 'unexpected hit'. Can be used when the loanword feels too casual.
その小説は予想外のヒットとなり、ベストセラーになった。
The novel became an unexpected hit and turned into a bestseller.
A spy or secret agent who lives normally for a long time until activated for a mission.
The direct loanword used in espionage contexts. Widely understood from movies and novels.
彼は長年スリーパーとして敵国に潜伏していた。
He had been living in the enemy country as a sleeper agent for years.
A more formal Japanese term meaning 'dormant operative'. Used in intelligence or military contexts.
その組織は複数の休眠工作員を国内に配置していると言われている。
The organization is said to have placed several sleeper agents within the country.
The word 寝る人 (ねるひと) only means 'a person who sleeps'. It cannot be used for a spy or an unexpected hit. Use the loanword スリーパー or the specific terms given above.
Literally 'dark horse', used for a little-known competitor or product that unexpectedly wins or succeeds. More common in sports or competition contexts.
あの新人歌手はダークホース的存在で、一気にスターダムにのし上がった。
That new singer was a dark horse and shot to stardom overnight.